Stereodivergent Synthesis of 1,3-Dienes via Protodeboronation of Homoallenylboronic Esters

Vinylboronic esters and allylboronic esters are well known to afford olefins by protodeboronation, and therefore homoallenylboronic esters should be similarly available as precursors for 1,3-dienes, but this strategy has not been well explored due to the limited availability of homoallenylboronic esters. Here, we describe a versatile synthesis of homoallenylboronic esters via lithiation–borylation and subsequent 1,2-rearrangement. The resulting homoallenylboronic esters were successfully converted into Z- and E-1,3-dienes by protodeboronation using Bu4NF and B­(C6F5)3/PhOH, respectively.