Nucleophilic attack on a carbonyl group conjugated to a chiral centre: a search for a vinylogous Cram's rule

Abstract

In a search for a vinylogous version of Cram's rule, 1,4-diphenylbut-2-ene-1,4-dione ( 5 ) , 4-rnethoxy-1,4-diphenylbut-2-en-l -one (9), and hex-3-ene-2,5-dione (13) are found to be reduced with low or negligible diastereoselectivity. Similarly, the phenyl Grignard reagent showed no diastereoselectivity in its reaction with 4-methoxy-4-phenylbut-2-enal (1 2)

Cationic Rhodium(I)/Bisphosphane Complex‐Catalyzed Isomerization of Secondary Propargylic Alcohols to α,β‐Enones

“…The residue was purified by silica gel column chromatography (hexane/ EtOAc, 10:1), which furnished alcohol 8a (1. Alcohol 8d: [39] To a stirred suspension of NaH (55 % in paraffin oil, 1.1 g, 44.0 mmol) in THF (40 mL) was added a THF (5 mL) solution of 1-phenylprop-2-yn-1-ol (2.6 g, 20.0 mmol) at room temp., and the resulting mixture was stirred at room temp. for 30 min.…”

Synthesis and Diastereoselective Reactions of N,N-Dibenzylamino Aldehydes and Related Compounds

“…The question of the so-called vinylogous Cram/anti Cram selectivity crops up occasionally in the literature, but systems capable of appreciable diastereoselectivity are rare . The first successful efforts directed toward achieving such remote asymmetric induction were based on α , β -unsaturated aldehydes 285 , which can be considered to be the vinylogs of aldehydes 10 .…”

The control of remote asymmetric centres via reduction of acyclic carbonyl functions

“…9). This followed a "vinylogous Cram's rule" as discussed and sought by Fleming et al 47 In related studies, Pyne et al recently demonstrated that high 1,5-diastereoselectivity could be achieved in the reduction of γ-keto-vinyl sulfoximine 97 with L-Selectride  48 (Scheme 28).…”