Asymmetric Claisen Rearrangements on Chiral Vinyl Sulfoxides

Abstract

Highly diastereoselective Claisen rearrangements of acyclic allyl vinyl ethers bearing a chiral sulfoxide at C-5 provide gamma-delta-unsaturated aldehydes or ketones with up to two consecutive asymmetric centers in the molecule whilst preserving a useful vinyl sulfoxide. The reactivity of related vinyl sulfides and sulfones has also been examined in this work.

Sulfinyl-Mediated Stereoselective Overman Rearrangements and Diels–Alder Cycloadditions

“…16,17 A relevant example of these methodologies was the highly diastereoselective Claisen rearrangement of enol ethers B to carbonyl derivatives C that brought about the generation of up to two stereogenic centers with preservation of a useful vinyl sulfoxide and with good control of the geometry of the alkene. 18 Within this context we decided to test the viability of the preparation of trichloroacetimidates D and their Overman rearrangement to allylic trichloroacetamides E with a stereodefined alkenyl sulfoxide moiety. The main aspects to be examined in this study were the geometry of the starting alkene, the relative stereochemistry of the chiral centers, and the nature of representative R 1 and R 2 groups in substrates A.…”

“…Our group has pursued new methodologies involving readily available α-hydroxy vinyl sulfoxides A (Scheme ). , A relevant example of these methodologies was the highly diastereoselective Claisen rearrangement of enol ethers B to carbonyl derivatives C that brought about the generation of up to two stereogenic centers with preservation of a useful vinyl sulfoxide and with good control of the geometry of the alkene . Within this context we decided to test the viability of the preparation of trichloroacetimidates D and their Overman rearrangement to allylic trichloroacetamides E with a stereodefined alkenyl sulfoxide moiety.…”

Enantiopure sulfoxides: recent applications in asymmetric synthesis

“…Ferna´ndez de la Pradilla and co-workers reported the diastereoselective Claisen rearrangements of acyclic allyl vinyl ethers such as (E,E)-vinyl p-tolylsulfinyl acrylate 43, to provide g-p-tolylsulfinyl-g,d-unsaturated aldehyde 45 (Scheme 9), 33 after heating and concurrent decarboxylation, with excellent diastereomeric excess. The stereoselectivity could be inverted starting from the (Z,E)-vinyl sulfinyl acrylate 44 which gave 46 with the best stereoselectivity when the sulfoxide had a 2-methoxynaphthyl substituent.…”

Sulfoxide-Directed Intramolecular [4 + 2] Cycloadditions between 2-Sulfinyl Butadienes and Unactivated Alkynes

“…In recent years, we have been involved in the development of different strategies for the synthesis of enantiopure hydroxy sulfinyl dienes, and we have carried out a general study of their intermolecular Diels−Alder reactivity . To extend this study, we decided to test the intramolecular Diels−Alder (IMDA) variant using 2-sulfinyl dienes A , and we focused our attention on the cycloadditions of dienynes B (Figure ) to produce cyclohexa-1,4-dienes C , which preserve a synthetically useful vinyl sulfoxide. , In the absence of a sulfinyl moiety, IMDA cycloadditions of this class of dienynes generally requires harsh thermal conditions that limit their application in synthesis. The use of transition metal catalysts provides a useful alternative affording cyclohexa-1,4-dienes by a different mechanism .…”