The Reactions of Primary Nitroparaffins with Isocyanates1

Natural Product Synthesis via 1,3‐Dipolar Cycloadditions

The synthesis of coumarins through Knoevenagel condensation is one of the mostimportant processes in synthetic organic chemistry and medicinal chemistry. Compoundsincluding a coumarin (2-oxo-2H-1-benzopyran) backbone have a wide range of applicationin the pharmaceutical ﬁeld. Thus, many methodologies havebeen developed for the synthesisof this important class of compounds. However, some methods are always associated withtoxic and corrosive catalysts, longer reaction time, poor yield, less purity, and by-productsalong with the desired product. Furthermore, some of these processes are not efﬁcient andenvironmentally friendly. Therefore, mild, efﬁcient, and environmentally friendly protocolshave been developed recently by many scientists for the synthesis of coumarin derivatives viaKnoevenagel condensation with good yield and purity. In this review, we have summarizedvarious methods for the synthesis of coumarins via Knoevenagel condensation.Keywords Coumarin derivatives; efﬁcient method; heterogeneous catalysts; high yield;ionic liquid; Knoevenagel condensation; piperidineReceived May 11, 2014.Address correspondence to Hitesh D. Patel, Department of Chemistry, School of Sciences, GujaratUniversity, Ahmedabad, India. E-mail: drhiteshpatel1@gmail.comColor versions of one or more of the ﬁgures in the article can be found online at www.tandfonline.com/lsyc.Synthetic Communications

Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic

N-substituted 5-methylene-2,3,4,5-tetrahydrobenzo[f][1,2]thiazepine 1,1-dioxides underwent 1,3-dipolar cycloaddition with benzonitrile oxide, generated in situ, to give isoxazoline spiro adducts. The cycloadditions were completely regioselective to give the hitherto unreported 3,4-dihydro-2H,4′H-spiro[benzo[f][1,2]thiazepine-5,5′-isoxazole] 1,1-dioxide cycloadduct. Where the N-substituent on the sulfonamide cycloaddition precursor was a 2-substituted arene, the resulting atropisomerism along the N-aryl bond led to facial selectivity in the cycloaddition reaction, with greater than 90 % diastereoselectivity.

Benzonitrile Oxide Cycloadditions with Exocyclic Methylene Benzothiazepine Dioxides

Isoxazoles, isoxazolines and isoxazolidines are a class of heterocyclic compounds having a remarkable number of applications and are very versatile building blocks in organic synthesis. The developments concerning the synthesis of the above monocyclic systems reported in the literature from 2007 to 2019 are reviewed. Some data related to theoretical methods, experimental structural methods, and thermodynamic aspects for this class of heterocycles are also reported. 

Isoxazoles

In the title compound, C17H22N2O4S, a thio­piperidine derivative, the piperidine ring has an envelope conformation with the methyl­ene C atom opposite to the C=S bond as the flap. The nitro­methyl substituent is equatorial while the eth­oxy­carbonyl group is axial. The mean planes of the nitro­methyl group, the carb­oxy group and phenyl ring are inclined to the mean plane through the five planar atoms of the piperidine ring [maximum deviation = 0.070 (4) A] by 56.8 (2), 83.8 (5) and 87.1 (2)°, respectively. There is an intra­molecular C—H⋯O hydrogen bond involving an H atom of the eth­oxy­carbonyl group and a nitro O atom. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by further C—H⋯O hydrogen bonds, forming corrugated layers lying parallel to (001).

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https://journals.iucr.org/e/issues/2015/01/00/su5036/su5036.pdf

The Reactions of Primary Nitroparaffins with Isocyanates1

Citations

Natural Product Synthesis via 1,3‐Dipolar Cycloadditions

Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic

Benzonitrile Oxide Cycloadditions with Exocyclic Methylene Benzothiazepine Dioxides

Isoxazoles

Crystal structure of (2S,4R)-ethyl 4-nitromethyl-1-[(S)-1-phenylethyl]-6-sulfanylidenepiperidine-2-carboxylate

Related Papers (5)

The isoxazoline route to the molecules of nature

1,3-Dipolar Cycloaddition Chemistry

The Nitrile Oxides

Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis

Asymmetric 1,3-Dipolar Cycloaddition Reactions

The Reactions of Primary Nitroparaffins with Isocyanates1

Citations

Natural Product Synthesis via 1,3‐Dipolar Cycloadditions

Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic

Benzonitrile Oxide Cycloadditions with Exocyclic Methylene Benzothiazepine Dioxides

Isoxazoles

Crystal structure of (2S,4R)-ethyl 4-nitro­methyl-1-[(S)-1-phenyl­eth­yl]-6-sulfanyl­idene­piperidine-2-carboxyl­ate

Related Papers (5)

The isoxazoline route to the molecules of nature

1,3-Dipolar Cycloaddition Chemistry

The Nitrile Oxides

Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis

Asymmetric 1,3-Dipolar Cycloaddition Reactions

Crystal structure of (2S,4R)-ethyl 4-nitromethyl-1-[(S)-1-phenylethyl]-6-sulfanylidenepiperidine-2-carboxylate