Use of mesityllithium in the α-alkylation reaction of β-alkyl-9-borabicyclo[3.3.1]nonanes

Abstract

Reaction of a-chloro and a-bromo esters with B-alkyl  9-borabicyclo[3.3.l]nonanes, B-alkyl-9-BBN, in the presence of the bulky carbon base, mesityllithium, was studied. The tnalkylboranes containing primary B-akyl groups reacted readily to give the corresponding esters. However, the reaction of trialkylboranes containing secondary B-alkyl groups was sluggish. The product esters were isolated by a non-oxidative workup. Use of mesityllithium in this a-alkylation reaction permitted trapping of the intermediate boron ester enolate using benzaldehyde. However, the aldol product thus obtained was a mixture of syn and anti isomers