An Asymmetric Vinylogous Michael Cascade of Silyl Glyoximide, Vinyl Grignard, and Nitroalkenes via Long Range Stereoinduction

Abstract

A diastereoselective auxiliary-mediated vinylation/[1,2]-Brook rearrangement/vinylogous Michael cascade of silyl glyoximide, vinylmagnesium bromide, and nitroalkenes is described. The reaction occurs with complete regio- and diastereocontrol in good yield. The diastereoselectivity is induced by a rare instance of 1,7-chirality transfer that is hypothesized to arise from a trans-multihetero-decalin transition state.

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

“…In 2016, Boyce and Johnson reported an example of stereoselective auxiliary-driven vinylogous Michael cascade exploiting silylglyoximide 886 as latently chiralized pronucleophile and nitroalkenes 887 as the acceptor partners (Scheme 224). 582 The in situ formation of the Z magnesium dienolate 886′ was initiated by vinylation of acyl silane 886, followed by [1,2]-Brook rearrangement (the carbon-to-oxygen silyl migration); then the dienolate 886′ coupled to nitroalkenes 887, thus terminating the vinylogous Michael cascade. The threecomponent reaction sequence yielded functionality-rich Z-silyl enol ethers 888 with complete chemo-(only traces of Grignard addition to nitroalkene were detected), regio-(only γ-adducts were observed), and facial selectivity (>20:1 diastereomeric ratio).…”

CuI‐Catalysed Enantioselective Alkyl 1,4‐Additions to (E)‐Nitroalkenes and Cyclic Enones with Phosphino‐Oxazoline Ligands

“…Cu‐catalysed enantioselective conjugate additions to nitroalkenes using organozinc reagents as the source of alkyl nucleophiles have been well investigated since first reports appeared , . Among the protocols that have been reported for the construction of tertiary carbon stereogenic centres, the representative examples shown in Scheme give high stereoselectivities and have broad substrate scopes.…”

Nitroalkenes as Latent 1,2-Biselectrophiles – A Multicatalytic Approach for the Synthesis of 1,4-Diketones and Their Application in a Four-Step One-Pot Reaction to Polysubstituted Pyrroles

“…All aldehydes are commercially available and were distilled under reduced pressure prior to use. All nitroalkenes are commercially available; however, nitroalkenes 9e – h , k , m , 9i , j , and 9l were prepared according to published protocols. Triazolium salt A is commercially available.…”