Organocatalytic Asymmetric Domino [3+2]-Cycloaddition-Acyl Transfer Reaction between Azomethine Ylides and α-Nitro-α,ß-Unsaturated Ketones.

Herein we have developed an organocatalytic asymmetric domino [3+2]-cycloaddition-acyl transfer reaction between in situ generated azomethine ylides and α-nitro-α,ß-unsaturated ketones. The desired penta-substituted pyrrolidine products were obtained in high yields and in moderate to good enantio- and diastereoselectivities. Also, an isomerization reaction in silica gel was performed for the formation of another diastereomer in high yields with retention of enantioselectivities.

DBU-Mediated Addition of α-Nitroketones to α-Cyano-enones and α,ß-Unsaturated α-Ketoesters: Synthesis of Dihydrofurans and Conjugated Dienes.

1,8-Diazabicyclo[5.4.0]undec-7-ene-mediated reactions of α-nitroketones with α-cyano-enones and α,ß-unsaturated α-ketoesters have been developed. The products, namely, dihydrofurans and conjugated dienes, were isolated in moderate to good yields, and a range of substitutions were tolerated.

Synthesis of N-Formyl-2-benzoyl Benzothiazolines, 2-Substituted Benzothiazoles, and Symmetrical Disulfides from N-Phenacylbenzothiazolium Bromides.

An unusual aerobic hydrolysis-cascade reaction has been developed with N-phenacylbenzothiazolium bromides by treatment with organic and inorganic base. The corresponding N-formyl-2-benzoyl benzothiazoline and 2-substituted benzothiazole products were obtained in moderate to good yields under mild reaction conditions. Also, symmetrical disulfide was formed when keto group was replaced with ester. The scopes of the reactions are fairly broad tolerating aryl, heteroaryl, and alkyl groups.

Organocatalytic Asymmetric Michael-Hemiacetalization Reaction Between 2-Hydroxyacetophenones and Enals: A Route to Chiral ß,γ-Disubstituted γ-Butyrolactones.

The first highly enantioselective organocatalytic reaction employing 2-hydroxyacetophenones is disclosed, namely Michael-hemiacetalization reaction of 2-hydroxyacetophenones with enals. The combination of a primary amine and a secondary amine catalyst was found to be the best choice for this methodology. The products of this reaction were obtained in high enantio- and diastereoselectivities and were converted to a variety of biologically important γ-butyrolactones.