Photochemically promoted transition metal-free cross-coupling of acylsilanes with organoboronic esters.

Intermolecular carbon-carbon bond formation between acylsilanes and organoboronic esters was achieved by photoirradiation under almost neutral, transition metal-free conditions. In this reaction, siloxycarbenes generated by photoisomerization of acylsilanes reacted with boronic esters to give the formal B-C bond insertion intermediates, which underwent unique rearrangement to afford the cyclic α-alkoxyboronic esters. Acidic treatment of the resulting crude products under air furnished the cross-coupled ketones in good yields.

Theoretical study of the cycloaddition reaction of a tungsten-containing carbonyl ylide.

The [3+2] cycloaddition reaction of a tungsten-containing carbonyl ylide with methyl vinyl ether and the insertion reactions of the nonstabilized carbene complex intermediates produced have been investigated through the use of B3LYP density functional theory. The [3+2] cycloaddition reaction of the tungsten-containing carbonyl ylide has been proven to proceed concertedly, reversibly, and with high endo selectivity. The intermolecular Si-H insertion reactions of the carbene complex intermediates have been proven to be favored over the intramolecular C-H insertion, in good agreement with experimental results. Moreover, the kinetic endo/exo ratio of the [3+2] cycloaddition reaction has been shown to determine the endo/exo selectivity of the Si-H insertion products. In addition, secondary orbital interactions involving the benzene ring and the carbonyl ligand on the metal center have turned out to strongly influence the high endo selectivity of the [3+2] cycloaddition reaction with methyl vinyl ether.