Photochemistry of Divinylboranamines

Article abstract of DOI:10.1021/ja00390a024

The photochemistry of the divinylboranamines was expolred in order to define structure-photoreactivity relationships of unsaturated organoboranes.Ultraviolet irradiation of the N,N-dimethyldivinylboranamines in cyclohexane gave cis-trans isomerization about the carbon-carbon double bonds to approximately statistical distribution of the three possible geometric isomers.Photolysis of the N-phenyldivinylboranamines gave nonoxidative photocyclization to azaboranaphthalenes in high yields.An investigation into the scope of cyclization revealed that chloro and bromo substituents were tolerated on the aromatic ring, while compounds with methyl, ethyl and tert-butyl groups on the vinyl moieties cyclized without difficulty.Quantum yields of cyclization ranged from 0.06 to 0.34 mol einstein ^-1.Photoproduct structure determinations were accomplished from spectroscopic data and chemical degradation reactions.Cyclization was found to occur in a variety of solvents including pentane, cyclohexane, dioxane and acetonitrile.In carbon tetrachloride, a carbon-boron bond-cleavage reaction occured, giving an N-phenylvinylchloroboranamine as the only identifiable photoproduct.A new synthetic route for selective ortho-alkylation of anilines was developed via divinylboration, photocyclization, protonolysis, and hydrolysis.The alkylation is comparable in yields to known methods and tolerates introduction of a wide variety of alkyl groups.