It was found that the reaction of thioboronites with carbonyl compounds and ketene proceeds with the initial formation of vinyloxyboranes (VII). The boranes were found to be important intermediates for the formation of β-hydroxythiolesters by the reaction with various carbonyl compounds. Vinyloxyborane derivatives can be alternatively prepared by the reactions of trialkylboranes and α-diazocarbonyl compounds. The boranes similarly ...