The synthesis of a bifunctional allylboron reagent via Ni-catalyzed borylation of allylic acetate is developed. Subsequent allylation of aldehydes, ketones and cyclic aldimines gave homoallylic alcohols and amines in good yields. The allylsilane moiety in the products serves as a useful handle for subsequent transformations.
The enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via phosphoric acid catalysis is developed. Both (E)- and (Z)-γ-borylmethyl allylboronate reagents were prepared via the Cu-catalyzed highly stereoselective protoboration of 1,3-dienylboronate. Chiral phosphoric acid-catalyzed aldehyde allylation with either the (E)- or (Z)-allylboron reagent provided 1,2-anti- or 1,2-syn-adducts in good yields with high enantioselectivities. The application to the synthesis of morinol D was accomplished.
A highly stereoselective synthesis of (E)-𝛿-boryl-anti-homoallylic alcohols is developed. In the presence of a Lewis acid, aldehyde allylation with 𝛼-boryl-(E)-crotylboronate gave 𝛿-boryl-anti-homoallylic alcohols in good yields with excellent E-selectivity. The E-vinylboronate group in the products provides a useful handle for cross-coupling reactions as illustrated in the fragment synthesis of chaxamycins C and D.
Highly stereo- and enantioselective synthesis of (E)-δ-hydroxymethyl-anti-homoallylic alcohols is developed. Under the developed conditions, reactions between aldehydes and chiral nonracemic α-borylmethyl-(E)-crotylboronate with oxidative workup gave δ-hydroxymethyl-anti-homoallylic alcohols with high E-selectivities and enantioselectivities.||en_US