Nickel-Catalyzed Double Bond Transposition of Alkenyl Boronates for in Situ syn-Selective Allylboration Reactions

Abstract

The transposition of a homoallyl pinacol boronic ester was realized by a highly reactive nickel-catalyst system comprising NiCl2(dppp), zinc powder, ZnI2, and Ph2PH. The in situ generated Z-crotyl pinacol boronic esters were reacted with various aldehydes to form syn-homoallylic alcohols in high diastereoselectivities. The present nickel-catalyzed reaction is complementary to the iridium-catalyzed transposition reported by Murakami leading to the corresponding anti-homoallylic alcohols. Also, the multiple transposition of pentenyl pinacol boronic ester was realized.

Selective Isomerization of Terminal Alkenes to (Z)-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex

“…Although no conversion was observed using 5p , the reaction of 5p·HCl proceeded using 0.5 mol % of 3-cis and 5 mol % of TsOH to generate 6p·HCl (79% yield, 1.3:1 Z : E ). 2-(But-3-en-1-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane ( 5q ) is a potential nucleophile yet still undergoes facile isomerization to yield the synthetically valuable allyl boronate ester 6q (74% yield, 7.7:1 Z : E ). The 1,5-diene 5r , featuring both internal and terminal alkene groups, is isomerized selectively to the ( Z , Z )-2,5-diene 6r (60%, 2:1 Z : E ) with no evident isomerization of the internal alkene.…”

Diastereo-, Enantio-, and anti-Selective Formation of Secondary Alcohol and Quaternary Carbon Stereocenters by Cu-Catalyzed Additions of B-Substituted Allyl Nucleophiles to Carbonyls

“…Homoallylic alcohols comprising a vicinal carbon stereocenter can be prepared by catalytic additions of substituted allyl fragments to aldehydes; − however, related transformations that deliver quaternary carbon stereogenic centers enantio- and diastereoselectively are difficult. While there are many examples for the construction of quaternary stereocenters via aldehyde allylation, few enantioselective methods exist. Prior disclosures include the enantiospecific intermolecular addition reactions of allylzincs derived from enantioenriched alkynylsulfoxides, as well as transformations with enantioenriched allylsilanes and allylboronic esters .…”

Nickel-Catalysed Allylboration of Aldehydes

“…14 Our results also complement reports of Ni-catalysed reductive allylations of carbonyls 15 and Ni-catalysed allylations via double bond transposition of alkenyl borates. 16…”