Applications of aryl-sulfinamides in the synthesis of N-heterocycles

Recent Advances in Asymmetric Synthesis of Pyrrolidine-Based Organocatalysts and Their Application: A 15-Year Update

In 1971, chemists from Hoffmann-La Roche and Schering AG independently discovered a new asymmetric intramolecular aldol reaction catalyzed by the natural amino acid proline, a transformation now known as the Hajos-Parrish-Eder-Sauer-Wiechert reaction. These remarkable results remained forgotten until List and Barbas reported in 2000 that L-proline was also able to catalyze intermolecular aldol reactions with non-negligible enantioselectivities. In the same year, MacMillan reported on asymmetric Diels-Alder cycloadditions which were efficiently catalyzed by imidazolidinones deriving from natural amino acids. These two seminal reports marked the birth of modern asymmetric organocatalysis. A further important breakthrough in this field happened in 2005, when Jørgensen and Hayashi independently proposed the use of diarylprolinol silyl ethers for the asymmetric functionalization of aldehydes. During the last 20 years, asymmetric organocatalysis has emerged as a very powerful tool for the facile construction of complex molecular architectures. Along the way, a deeper knowledge of organocatalytic reaction mechanisms has been acquired, allowing for the fine-tuning of the structures of privileged catalysts or proposing completely new molecular entities that are able to efficiently catalyze these transformations. This review highlights the most recent advances in the asymmetric synthesis of organocatalysts deriving from or related to proline, starting from 2008.

Diastereoselective Synthesis of trans-β-Amino Cyclohexyl Ketones and trans-3-Amino-4-acyl-tetrahydropyrans from Intramolecular C-Alkylation of ω-Halo-Substituted β-Sulfinamido Ketones

Reaction of ω-halo-substituted nonracemic β-sulfinamido ketones with NaH afforded the β-amino cyclohexyl ketones in excellent yields and diastereoselectivity, via an intramolecular C-alkylation, α to the carbonyl group. The reaction was found to be general and can be applied for the synthesis of different cyclohexyl amino ketones and tetrahydropyrans possessing amine and acyl substitutions.

Diastereoselective Hydroxylation of N-tert-Butanesulfinyl Imines with 2-(Phenylsulfonyl)-3-phenyloxaziridine (Davis Oxaziridine)

The diastereoselective α-hydroxylation of N-tert-butanesulfinyl metallodienenamine and metalloenamines with Davis oxaziridine affords α-hydroxy N-sulfinyl imines with 50-88% yield and up to 98:2 diastereomeric ratio. Dramatic changes in diastereoselectivity and stereoselectivity were observed by choice of metal bases. The mechanistic understanding for the switch in diastereoselectivity was assisted by DFT computational modeling, which suggests the facial approach is governed by aza-enolate geometry. A one-pot protocol for the asymmetric synthesis of 1,2-amino alcohols is described.

Photocatalytic Synthesis of Sulfinamides and Sulfoxides from Nitroarenes and Thiophenols

We present an efficient and versatile visible light-driven methodology for synthesizing sulfinamides and sulfoxides using nitroarenes as the nitrogen source and thiophenols as the sulfur source. The switch-over of the two reaction pathways was achieved by changing the type of photocatalyst and the amount of thiophenol in the reaction mixture. The reaction proceeds under mild conditions with good functional group tolerance and can easily be scaled up.