AUTHOR OF THIS BLOG

DR ANTHONY MELVIN CRASTO, WORLDDRUGTRACKER
Oct 162017
 

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Diethyl Isosorbide (DEI): []D 20 +95.9 (c 1, in MeOH);

1H NMR (400 MHz; CDCl3; Me4Si):  4.63 (t, J = 4.2 Hz, 1H, H-4), 4.51 (d, J = 4.1 Hz, 1H, H-3), 4.06–3.90 (m, 5H, H- 1, H-2, H-5, H-6), 3.80–3.69 (m, 1H, CH2-OC-5), 3.63–3.49 (m, 4H, H-6, CH2-OC-5, CH2- OC-2), 1.23 ppm (dt, J = 17.8, 7.0 Hz, 6H, CH3CH2O-C-2, CH3CH2O-C-5);

13C NMR (101 MHz; CDCl3; Me4Si):  86.57 (C-3), 84.45 (C-2), 80.36 (C-5), 80.27 (C-4), 73.64 (C-1), 69.81 (C-6), 66.28 (CH2-O-C-5), 65.24 (CH2-O-C-2), 15.49 ppm (CH3-CH2OC-5), 15.44 (CH3-CH2OC-2);

MS (70 eV): m/z 202 (M+ , 6%), 157 (1), 113 (17), 89 (33), 69 (100), 57 (11), 44 (39).

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Oct 162017
 

 

 

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC01912B, Tutorial Review
C. Dussenne, T. Delaunay, V. Wiatz, H. Wyart, I. Suisse, M. Sauthier
This review gives an overview of the catalysts and technologies developed for the synthesis of isosorbide, a platform molecule derived from biomass (sorbitol and cellulose).

Synthesis of isosorbide: an overview of challenging reactions

 Author affiliations

Abstract

Isosorbide is a diol derived from sorbitol and obtained through dehydration reactions that has raised much interest in the literature over the past few decades. Thus, this platform chemical is a biobased alternative to a number of petrosourced molecules that can find applications in a large number of technical specialty fields, such as plasticizers, monomers, solvents or pharmaceuticals. The synthesis of isosorbide is still a technical challenge, as several competitive reactions must be simultaneously handled to promote a high molar yield and avoid side reactions, like degradation and polymerization. In this purpose, many studies have proposed innovative and varied methods with promising results. This review gives an overview of the synthesis strategies and catalysts developed to access this very attractive molecule, pointing out both the results obtained and the remaining issues connected to isosorbide synthesis.

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Up to now, isosorbide has been used to access a large panel of molecules with relevant applicative properties and industrial reality (Scheme 2).12 Isosorbide dinitrate is used since several decades as vasodilator.13, 14 The dimethyl isosorbide is for example used as solvent in cosmetics15-17 and isosorbide diesters18-22 are actually industrially produced and commercialized as surfactants23-27 and PVC plasticizer28, 29 . The rigid scaffold associated to the bifunctionality of the molecule has attracted a strong interest in the field of polymers chemistry. Isosorbide and derivatives have thus been shown as suitable monomers for the industrial production of polycarbonates30, 31, polyesters32-41 or polyamides42-44, with attractive applicative properties. For example, isosorbide allows the increase of Tg, improves the scratch resistance and gives excellent optical properties to polymers. Polyesters and polycarbonates containing isosorbide have now commercial developments in food packaging, spray container, automotive, material for electronic devices … .

Conclusions

Isosorbide is a versatile platform molecule that shows key features to make it a credible alternative to petro-based products. The molecule is already available on large industrial scale (tens of thousands tons per years), which allows its development in commercial products such as active pharma ingredient, additive for cosmetic, speciality chemicals and polymers (ex: polycarbonates – polyesters). The development of more selective and higher yields syntheses of isosorbide are greatly needed to consolidate isosorbide production in view of a large expansion of its uses. Sorbitol conversion to isosorbide, relying on a starch route, is already a tough challenge. In a farther future, development of a credible path to isosorbide relying on cellulose source could even be thought of, provided that very versatile innovative catalysts will be developed in the next years. In all cases, a key issue is to develop catalysts that will avoid the massive production of “oligomeric/polymeric” by-products in order to access more sustainable processes by limiting the amounts of wastes produced during the synthesis. For this purpose, more selective homogeneous catalysts than the conventional Brønsted acids or alternative reaction conditions would be of strong interest. Selective and recyclable heterogeneous catalysts would be even more profitable as they would allow the continuous production of catalyst free isosorbide. This latter approach faces strong limitations due to the need of high reaction temperatures that often result in high amounts of side-products and the need of frequent and often tedious catalyst regeneration. Innovation concerning isosorbide synthesis is still an open field on which the design of efficient and robust catalysts, either homogeneous or heterogeneous, is a key issue. Such developments would pave the way to high scale effective processes considering altogether synthesis and purification of isosorbide.

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Isosorbide is a heterocyclic compound that is derived from glucose. Isosorbide and its two isomers, namely isoidide and isomannide, are 1,4:3,6-dianhydrohexitols. It is a white solid that is prepared from the double dehydration of sorbitol. Isosorbide is a non-toxic diolproduced from biobased feedstocks, that is biodegradable and thermally stable. It is used in medicine and has been touted as a potential biofeedstock.

Production

Hydrogenation of glucose gives sorbitol. Isosorbide is obtained by double dehydration of sorbitol:

(CHOH)4(CH2OH)2 → C6H10O2(OH)2 + 2 H2O

An intermediate in the dehydration is the monocycle sorbitan.[1]

Application

Isosorbide is used as a diuretic, mainly to treat hydrocephalus, and is also used to treat glaucoma.[2] Other medications are derived from isosorbide, including isosorbide dinitrate and isosorbide mononitrate, are used to treat angina pectoris. Other isosorbide-based medicines are used as osmotic diuretics and for treatment of esophageal varices. Like other nitric oxide donors (see biological functions of nitric oxide), these drugs lower portal pressure by vasodilation and decreasing cardiac output. Isosorbide dinitrate and hydralazineare the two components of the anti-hypertensive drug isosorbide dinitrate/hydralazine (Bidil).

Isosorbide is also used as a building block for bio based polymers such as polyesters.[3]

References

  1. Jump up^ M. Rose, R. Palkovits (2012). “Isosorbide as a Renewable Platform chemical for Versatile Applications—Quo Vadis?”. ChemSusChem5 (1): 167–176. PMID 22213713doi:10.1002/cssc.201100580.
  2. Jump up^ CID 12597 from PubChem
  3. Jump up^ Bersot J.C. (2011). “Efficiency Increase of Poly (ethylene terephthalate‐co‐isosorbide terephthalate) Synthesis using Bimetallic Catalytic Systems”. Macromol. Chem. Phys212 (19): 2114–2120. doi:10.1002/macp.201100146.
Isosorbide
Isosorbide.svg
Names
Other names

D-Isosorbide; 1,4:3,6-Dianhydro-D-sorbitol; 1,4-Dianhydrosorbitol
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.010.449
KEGG
PubChem CID
UNII
Properties
C6H10O4
Molar mass 146.14 g·mol−1
Appearance Highly hygroscopic white flakes
Density 1.30 at 25 °C
Melting point 62.5 to 63 °C (144.5 to 145.4 °F; 335.6 to 336.1 K)
Boiling point 160 °C (320 °F; 433 K) at 10 mmHg
in water (>850 g/L), alcoholsand ketones
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

From the net

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1H Nuclear magnetic resonance (NMR) spectra of PTMG, isosorbide, HDI, and polyurethane.HDI: hexamethylene diisocyanate; PTMG: poly(tetramethylene glycol).

1H Nuclear magnetic resonance (NMR) spectra of PTMG, isosorbide, HDI, and polyurethane.HDI: hexamethylene diisocyanate; PTMG: poly(tetramethylene glycol).

 

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REF

http://www.rsc.org/suppdata/gc/c4/c4gc01822b/c4gc01822b1.pdf

Synthesis of five- and six-membered heterocycles by dimethyl carbonate with catalytic amount of nitrogen bicyclic bases

http://pubs.rsc.org/en/content/articlelanding/2015/gc/c4gc01822b#!divAbstract

F. Aricò, a,*S. Evaristoa and P. Tundoa,*

Catalytic amount of a nitrogen bicyclic base, i.e., DABCO, DBU and TBD is effective for the one-pot synthesis of heterocycles from 1,4-, 1,5-diols and 1,4-bifunctional compounds via dimethyl carbonate chemistry under neat conditions. Nitrogen bicyclic bases, that previously showed to enhance the reactivity of DMC in methoxycarbonylation reaction by BAc2 mechanism, are herein used for the first time as efficient catalysts for cyclization reaction encompassing both BAc2 and BAl2 pathways. This synthetic procedure was also applied to a large scale synthesis of cyclic sugars isosorbide and isomannide starting from D-sorbitol and D-mannitol, respectively. The resulting anhydro sugar alcohols were obtained as pure crystalline compounds that did not require any further purification or crystallization.

Image result for ISOSORBIDE SYNTHESIS

Larger scale synthesis of isosorbide: In a round bottom flask equipped with a reflux condenser, D-sorbitol (0.05 mol, 1.00 mol. eq.), DMC (0.44 mol, 8.00 mol. eq.), DBU (2.70 mmol, 0.05 mol. eq.) and MeOH (20.00 mL) were heated at reflux while stirring. The progress of the reaction was monitored by NMR. After 48 hours the reaction was stopped, cooled at room temperature and the mixture was filtered over Gooch n°4. Finally, DMC was evaporated under vacuum and the product was obtained as pure in 98% yield (7.90 g, 0.05 mol). Characterization data were consistent with those obtained for the commercially available compound.

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Image result for ISOSORBIDE SYNTHESIS

File:Isosorbide dinitrate synthesis.png

 

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Oct 102017
 

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Total synthesis of (-)-aritasone via the ultra-high pressure hetero-Diels-Alder dimerisation of (-)-pinocarvone

Org. Biomol. Chem., 2017, Advance Article

DOI: 10.1039/C7OB02204B, Paper
Maliha Uroos, Phillip Pitt, Laurence M. Harwood, William Lewis, Alexander J. Blake, Christopher J. Hayes
The total synthesis of aritasone via the proposed biosyntheic hetero-Diels-Alder [4 + 2] cyclodimerisation of pinocarvove, has been achieved under ultra-high pressure (19.9 kbar) conditions

Total synthesis of (−)-aritasone via the ultra-high pressure hetero-Diels–Alder dimerisation of (−)-pinocarvone

 Author affiliations

Christopher Hayes

Abstract

This paper describes a total synthesis of the terpene-derived natural product aritasone via the hetero-Diels–Alder [4 + 2] cyclodimerisation of pinocarvove, which represents the proposed biosyntheic route. The hetero-Diels–Alder dimerisation of pinocarvone did not proceed under standard conditions, and ultra-high pressure (19.9 kbar) was required. As it seems unlikely that these ultra-high pressures are accessible within a plant cell, we suggest that the original biosynthetic hypothesis be reconsidered, and alternatives are discussed.

STR1 STR2
Aritasone (1) A solution of pinocarvone (()-2) (100 mg, 0.66 mmol) in dichloromethane (5 mL) was pressurized to 19.9 kbar for 120 h. The 1H NMR spectrum of the crude reaction mixture showed significant change in the composition as compared to the starting material. The solvent was evaporated and the residue was purified by column chromatography (pentane/Et2O; 25/1) to afford aritasone (1) (20 mg, 40%) as a white solid; mp 101- 103 C; (lit3 mp 105-106 °C); []D 26 26.1 (c 0.40 in CHCl3); (lit3 []D 9 118); max/cm-1 (CHCl3) 2926, 2359, 1722, 1689, 1601, 1467, 1372, 1305, 1152; H (400 MHz; CDCl3, 298 K) 2.67 (2H, app dd, J 4.8, 2.5, H-2a, H-2b), 2.45-2.32 (3H, m, H-7a, H-15a, H-3), 2.15-2.01 (4H, m, H-10, H-12, H-15b, H-16a), 1.91-1.80 (2H, m, H-4, H-16b), 1.66 (1H, ddd, J 13.8, 6.4, 3.4, H-7b), 1.38 (3H, s, CH3), 1.29-1.22 (7H, br s, CH3, H-13a, H-13b, H-8a, H- 8b), 0.90 (3H, s, CH3), 0.80 (3H, s, CH3); C (100 MHz; CDCl3, 298 K) 209.5 (C), 142.9 (C), 112.8 (C), 80.8 (C), 45.2 (CH), 44.3 (CH), 43.7 (CH2), 40.9 (CH), 40.5 (C), 39.4 (CH), 38.3 (C), 33.2 (CH2), 32.7 (CH2), 27.7 (CH3), 27.3 (CH2), 27.3 (CH3), 26.3 (CH3), 22.5 (CH2), 22.1 (CH2), 20.9 (CH3); HRMS m/z (ES+ ) found 301.2162 (M + H) C20H29O2 requires 301.2162 and 323.1981 (M + Na) C20H28O2Na requires 323.1982. These data were consistent to those previously reported, 5, 7 however the value of the specific rotation5 differs significantly from that measured during the original isolation work.3

Christopher Hayes

Contact

Biography

Prof. Christopher Hayes began his academic career here in Nottingham with his B.Sc. in July 1992. Remaining at Nottingham, he completed his Ph.D. studies in organic chemistry, under the supervision of Professor Gerald Pattenden, in September 1995. In January 1996, on a NATO Postdoctoral Fellowship, he moved to the University of California at Berkeley where he worked in the group of Professor Clayton H. Heathcock. In September 1997, he returned to Nottingham as a Lecturer in Organic Chemistry, and has subsequently been promoted to Reader (2003), Associate Professor (2006) and Professor of Organic Chemistry (2011).

Research Summary

Research is centred in main-stream synthetic organic chemistry, focusing on the organic chemistry of biologically active molecules. His current research interests span a number of areas such as (i)… read more

Recent Publications

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Oct 092017
 

 

Catal. Sci. Technol., 2017, Advance Article
DOI: 10.1039/C7CY01621B, Paper
Youming Ni, Lei Shi, Hongchao Liu, Wenna Zhang, Yong Liu, Wenliang Zhu, Zhongmin Liu
Halide-free and noble metal-free pyridine-modified H-mordenites exhibit high stability and selectivity in methanol carbonylation to acetic acid.

A green route for methanol carbonylation

 Author affiliations

Abstract

Acetic acid is one of the most important bulk commodity chemicals and is currently manufactured by methanol carbonylation reactions with rhodium or iridium organometallic complexes and halide-containing promoters named Monsanto or BP Cativa™ homogeneous processes, respectively. Developing a halide-free catalyst and a heterogeneous process for methanol carbonylation is of great importance and has recently attracted extensive research attention. Here, we report a green route for direct synthesis of acetic acid via vapor-phase carbonylation of methanol with a stable, selective, halide-free, and noble metal-free catalyst based on pyridine-modified H-mordenite zeolite. Methanol conversion and acetic acid selectivity can reach up to 100% and 95%, respectively. Only little deactivation is observed during the 145 hour reaction.

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Oct 092017
 

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A fully continuous-flow diazotization–hydrolysis protocol has been developed for the preparation of p-cresol. This process started from the diazotization of p-toluidine to form diazonium intermediate. The reaction was then quenched by urea and subsequently followed by a hydrolysis to give the final product p-cresol. Three types of byproducts were initially found in this reaction sequence. After an optimization of reaction conditions (based on impurity analysis), side reactions were eminently inhibited, and a total yield up to 91% were ultimately obtained with a productivity of 388 g/h. The continuous-flow methodology was used to avoid accumulation of the highly energetic and potentially explosive diazonium salt to realize the safe preparation for p-cresol.

 

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1H NMR (400 MHz, (CD3)2SO) δ/ppm: 9.06 (br s, 1H, −OH), 6.94 (d, J = 8.0 Hz, 2H, Ar–H), 6.62 (d, J = 8.0 Hz, 2H, Ar–H), 2.17 (s, 3H, −CH3).

13C NMR (CDCl3) δ/ppm: 153.0, 129.9, 115.1, 20.5.

 

Literature data:(3b) 1H NMR (300 MHz, CDCl3) δ/ppm: 7.03 (d, J = 8.2 Hz, 2H), 6.73 (dd, J = 8.2, 2.0 Hz, 2H), 4.75 (s, 1H, OH), 2.27 (s, 3H, CH3).

13C NMR (CDCl3) δ/ppm: 153.2, 130.2, 115.2, 20.6.

3(b) TaniguchiT.ImotoM.TakedaM.NakaiT.MiharaM.IwaiT.ItoT.MizunoT.NomotoA.OgawaA. Heteroat. Chem. 201526411– 416 DOI: 10.1002/hc.21275

A Fully Continuous-Flow Process for the Synthesis of p-Cresol: Impurity Analysis and Process Optimization

National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients, Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014, P. R. China
Org. Process Res. Dev., Article ASAP
DOI: 10.1021/acs.oprd.7b00250
*Tel.: (+86)57188320899. E-mail: pharmlab@zjut.edu.cn.

http://pubs.acs.org/doi/full/10.1021/acs.oprd.7b00250

 

NMR PREDICT

STR1 STR2

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Sep 292017
 

 

Total synthesis of natural products via iridium catalysis

Org. Chem. Front., 2017, Advance Article
DOI: 10.1039/C7QO00664K, Review Article
Changchun Yuan, Bo Liu
An overview of the highlights in total synthesis of natural products using iridium as a catalyst is given

http://pubs.rsc.org/en/Content/ArticleLanding/2017/QO/C7QO00664K#!divAbstract

Total synthesis of natural products viairidium catalysis

 Author affiliations

Abstract

Catalysis with transition metals is a powerful synthetic tool for achieving a high degree of molecular complexity from relatively simple building blocks. Among these transition metals employed, iridium has attracted significant attention owing to its multifold roles in catalysis of various synthetically significant methodologies, and thus iridium catalysts are widely used in natural product synthesis. This review aims to comprehensively summarize recent accomplishments in total synthesis of natural products using iridium as the catalyst.

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Image result for School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR ChinaImage result for School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR China

School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR China

Image result for College of Chemistry, Sichuan University, Chengdu

Image result for College of Chemistry, Sichuan University, Chengdu

Image result for College of Chemistry, Sichuan University, ChengduKey Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu

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Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

 spectroscopy, SYNTHESIS  Comments Off on Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines
Sep 202017
 

 

Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

Green Chem., 2017, 19,4036-4042
DOI: 10.1039/C7GC01494E, Communication
Mohit L. Deb, Choitanya D. Pegu, Paran J. Borpatra, Prakash J. Saikia, Pranjal K. Baruah
Synthesis of 1,3-oxazines via catalyst free C-H functionalization using molecular oxygen in water.

Catalyst-free multi-component cascade C–H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

 Author affiliations

Abstract

Herein, catalyst-free 3-component reactions of naphthols, aldehydes, and tetrahydroisoquinolines to synthesize 1,3-oxazines is reported. The reaction is performed in H2O in the presence of O2 as the sole oxidant at 100 °C, which proceeds through the formation of 1-aminoalkyl-2-naphthols followed by selective α-C–H functionalization of tert-amine.

15-phenyl-7a,12,13,15-tetrahydronaphtho[1′,2′:5,6][1,3]oxazino[2,3- a]isoquinoline (4a):1

White solid; Yield 61 %, 221 mg;

1H NMR (500 MHz, CDCl3): δ 7.79-7.77 (m, 1H), 7.74 (d, J = 8.9 Hz, 1H), 7.43-7.41 (m, 1H), 7.33-7.28 (m, 8H), 7.24-7.19 (m, 3H), 7.11 (d, J = 8.9 Hz, 1H), 5.65 (s, 1H), 5.44 (s, 1H), 3.40-3.26 (m, 2H), 3.12-3.09 (m, 1H), 2.90- 2.86 (m, 1H);

13C NMR (125 MHz, CDCl3): δ 151.9, 142.3, 135.0, 133.0, 132.4, 129.3, 129.1, 128.9, 128.8 (2C), 128.7, 128.6, 128.2, 127.4, 126.5, 126.2, 123.1, 122.7, 118.9, 110.9, 82.2, 62.6, 45.4, 29.4;

HRMS (ESI) exact mass calculated for C26H21NO [M+H]+ : 364.1701; found: 364.1705.

The representative procedure for the synthesis of 4a is as follows: 2-naphthol (1a, 144 mg, 1 mmol), benzaldehyde (2a, 106 mg, 1 mmol), tetrahydroisoquinoline (3, 133 mg, 1 mmol) and water (1.5 mL) were added in a round-bottom flask equipped with a magnetic stirring bar and a reflux condenser. The whole apparatus was efficiently flushed with oxygen gas and then connected to a balloon filled with oxygen. After vigorous stirring at 100 oC for 12 h, water was removed under vacuum and purified the reaction mixture by column chromatography (100-200 mesh silica gel, hexane-ethyl acetate) to obtain the product 4a as white solid. The other 1,3-oxazines were synthesized and purified by following the procedure described above

str4

STR7str6

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Efficient route for the construction of polycyclic systems from bioderived HMF

 spectroscopy, SYNTHESIS  Comments Off on Efficient route for the construction of polycyclic systems from bioderived HMF
Sep 162017
 

 

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02211E, Paper
F. A. Kucherov, K. I. Galkin, E. G. Gordeev, V. P. Ananikov
Efficient one-pot synthesis of tricyclic compounds from biobased 5-hydroxymethylfurfural (HMF) is described using a [4 + 2] cycloaddition reaction.

Efficient route for the construction of polycyclic systems from bioderived HMF

 Author affiliations

Abstract

The first synthesis of tricyclic compounds from biobased 5-hydroxymethylfurfural (HMF) is described. The Diels–Alder reaction was used to implement the transition from HMF to a non-planar framework, which possessed structural cores of naturally occurring biologically active compounds and building blocks of advanced materials. A one-pot, three-step sustainable synthesis in water was developed starting directly from HMF. The reduction of HMF led to 2,5-bis(hydroxymethyl)furan (BHMF), which could be readily involved in the Diels–Alder cycloaddition reaction with HMF-derived maleimide, followed by hydrogenation of the double bond. The described transformation was diastereoselective and proceeded with a good overall yield. The applicability of the chosen approach for the synthesis of analogous structures containing amine functionality on the side chain was demonstrated. To produce the target compounds, only platform chemicals were used with carbohydrate biomass as the single carbon source.

Endo-4,7-bis(hydroxymethyl)-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindole-1,3(2H)-dione (endo-4,7-bis(hydroxymethyl)norcantharimid-5-ene), 3

1H NMR (DMSO-d6) = 10.82 (s, 1H), 6.37 (s, 2H), 5.11 (t, 2H, J = 5.7 Hz), 3.97 (dd, 2H, J = 5.7 Hz, 12.8 Hz), 3.84 (dd, 2H, J = 5.7 Hz, 12.8 Hz), 3.44 (s, 2H);

13C NMR (DMSO-d6) = 176.9, 136.0, 92.1, 59.8, 48.8 ppm.

m/z HRMS (ESI) Calcd. for C10H11NO5 [M+Na]: 248.0529. Found 248.0536.

STR7

str4 str6

1H NMR PREDICT

 

str4

str4 str6

13C NMR PREDICT

 

str4 str6

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O=C1NC(=O)[C@H]3[C@@H]1[C@]2(C=C[C@]3(CO)O2)CO

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Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

 spectroscopy, SYNTHESIS  Comments Off on Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen
Sep 072017
 

Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02014G, Communication
Yanjun Xie, Xiangui Chen, Zhen Wang, Huawen Huang, Bing Yi, Guo-Jun Deng
Aerobic cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen under metal-free conditions.

Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

 

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC02014G?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Abstract

Metal-free oxidative cyclization for the one-pot synthesis of benzo[d]imidazo[2,1-b]thiazoles from 2-aminobenzothiazoles and cyclic ketones is described. Elemental sulfur combined with molecular oxygen as the benign co-oxidant was found to be unique and highly effective to promote this transformation without the aid of any metal salts. Various cyclic ketones smoothly reacted with 2-aminobenzothiazoles to give functional benzo[d]imidazo[2,1-b]thiazoles in good to very high yields, which thereby demonstrated the synthetic convergence of this methodology.

Graphical abstract: Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen
7,8,9,10-Tetrahydrobenzo[d]benzo[4,5]imidazo[2,1-b]thiazole (3a)
White solid; yield: 39.2 mg (86%), mp 140-142 °C.
STR1
1H NMR (400 MHz, CDCl3, ppm) δ 7.67-7.62 (m, 2H), 7.38 (t, J = 7.76 Hz, 1H), 7.27 (t, J = 7.68 Hz, 1H), 3.07-3.04 (m, 2H), 2.77-2.74 (m, 2H), 2.00-1.95 (m, 2H), 1.92-1.86 (m, 2H);
13C NMR (100 MHz, CDCl3, ppm) δ 145.1, 142.4, 132.9, 129.7, 125.5, 123.9, 123.5, 121.8, 111.9, 24.8, 22.8, 22.7, 21.8;
MS (EI) m/z (%) 228, 200 (100), 160, 108, 51;
HRMS calcd. for: C13H13N2S + (M+H)+ 229.07940, found 229.07941.
 STR2
str3
PREDICT
STR1
STR2
cas 325766-28-7
C13 H12 N2 S, 228.31,  Benzimidazo[2,​1-​b]​benzothiazole, 7,​8,​9,​10-​tetrahydro-

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C1CCCc2c1nc3sc4ccccc4n23

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