Chiral α-substituted allylboronic
acids were synthesized
by asymmetric homologation of alkenylboronic acids using CF
3
/TMS-diazomethanes in the presence of BINOL catalyst and ethanol.
The chiral α-substituted allylboronic acids were reacted with
aldehydes or oxidized to alcohols in situ with a high degree of chirality
transfer. The oxygen-sensitive allylboronic acids can be purified
via their isolated diaminonaphthalene (DanH)-protected derivatives.
The highly reactive purified allylboronic acids reacted in a self-catalyzed
reaction at room temperature with ketones, imines, and indoles to
give congested trifluoromethylated homoallylic alcohols/amines with
up to three contiguous stereocenters.
A one-pot approach to fluorinated hydroxamic acid, amide, and thioamide derivatives is reported. The reaction proceeds via an N-perfluoroalkylation of nitrosoarenes with perfluoroalkanesulfinates, resulting in labile N-perfluoroalkylated hydroxylamines. By the addition of suitable additives, a controllable oxy/thiodefluorination of the fluorinated hydroxylamine intermediates was achieved. The method highlights N-perfluoroalkylated amines as versatile intermediates for further synthesis.
We have developed a new three-component catalytic coupling
reaction
of alkynyl boronates, diazomethanes, and aliphatic/aromatic ketones
in the presence of BINOL derivatives. The reaction proceeds with a
remarkably high enantio- and diastereoselectivity (up to three contiguous
stereocenters) affording tertiary CF3-allenols in a single
operational step. The reaction proceeds under mild, neutral, metal-free
conditions, which leads to a high level of functional group tolerance.
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