Diastereoselective Conjugate Addition of Organocuprates to Chiral N-Enoyl Oxazolidinethiones

Abstract

Addition of organocuprates, generated in situ using an excess of a 1:2 mixture of CuI·DMS and Grignard reagent, to N-enoyl oxazolidinethiones in the presence of excess TMSI gave preferentially the anti diastereomer where the addition took place when the conformation of the substrate was syn-s-cis. The reaction was investigated with indene-based and three different phenyl glycine derived oxazolidinethiones.

Synthetic Applications of Sulfur-based Chiral Auxiliaries in Asymmetric Syntheses

“…In collaboration with Benemérita Universidad Autónoma de Puebla, we reported that addition of methylcuprates, generated in situ using an excess of a 1:2 mixture of CuI-DMS and the Grignard reagent to N-enoyl oxazolidinethione 18 in the presence of excess TMSI gave preferentially the anti-diastereomer 19. [38] This Michael addition took place when the conformation of the substrate was syn-s-cis.…”

Desulfurization–Oxygenation of Chiral 1,3-Thiazolidine-2-thiones and 1,3-Oxazolidine-2-thiones Using Propylene Oxide and Microwave Irradiation

“…Recently, we encountered some problems in the purification of the N-enoyl imide derivatives during our work on the 1,4-addition of organocuprates to N-enoyl thiazolidinethiones and oxazolidinethiones. 11 This problem was attributed to the high nucleophilicity of the sulfur atom present in the thiocarbonyl group reacting intramolecularly with the unsaturation during chromatography. Palomo described the rearrangement of the sulfur atom in the thiocarbonyl of N-enoyl oxazolidinethiones when Lewis acids are present.…”

NMR and Theoretical Studies on the Conformational Preferences of Some Non-metal Coordinated N-Enoyl Systems Attached to Common Chiral Auxilaries

“…More recently, Sabala et al [6] suggests that N-enoyloxazolidinone systems in an anti-s-cis conformation lead to syn addition products, whereas a syn-s-cis conformation lead to anti addition products. In both cases addition of the nucleophile always takes place on the face of the double bond opposite to the R group in the chiral auxiliary.…”