Regioselective Allene Synthesis and Propargylations with Propargyl Diethanolamine Boronates

The utility of propargyl diethanolamine boronates as reagents for the preparation of allenes and homopropargylic alcohols is presented. Protonolysis with TFA and electrophilic substitution with N-halosuccinimides proceeded with inversion to provide the corresponding allene in high yield and regioselectivity. Alternatively, the propargylation of aldehydes was achieved with use of the in situ generated lithiated complex.