Vinylborane

Vinylborane, also known as ethenylborane, is an organoboron compound with the structural motif CH2=CH–BH2. It is the simplest vinylborane and is used as a reactive building block in boron chemistry. The molecule consists of a vinyl group attached to a boron atom bearing two hydrogens; boron is typically three-coordinate with an empty p orbital, making the B–C bond reactive toward further transformations.

Preparation and handling: Vinylborane is typically generated in situ by the hydroboration of acetylene with a borane source such as diborane (B2H6) or trialkylboranes under strictly anhydrous and oxygen-free conditions. It is highly reactive and sensitive to air and moisture, so it is ordinarily prepared and consumed under inert atmosphere and stored only under appropriate inert solvents or as stabilized derivatives.

Reactions and applications: As a versatile vinyl boron reagent, vinylborane participates in several transformations. Oxidative workup of the B–H bonds gives vinylboronic acids (R–B(OH)2), which are common substrates for Suzuki–Miyaura cross-couplings to form alkenyl products. Vinylborane derivatives, such as vinylboronates, broaden the scope of cross-coupling and other boron‑mediated coupling strategies. In hydroboration‑based alkyne chemistry, vinylboranes arise from anti‑Markovnikov addition of boron to alkynes and can be elaborated to a variety of alkenyl boron reagents for further functionalization.

Related compounds and notes: Vinylborane is a reactive intermediate in organoboron chemistry and is typically handled under inert conditions. It relates to vinylboronic acids, vinyl boronates, and higher‑order boronates used in polymer and materials chemistry.