REACTIONS OF BORANES WITH AROMATIC AZIDES. III. A SIMPLE ROUTE TO 1,2-DIHYDRO-N-PHENYL,THIENO- AND THIENO-AZABORINES

Article abstract of DOI:10.1016/0022-328X(85)80299-0

Some halogeno(organyl)boranes have been formed to promote fragmenatation of organic azides, through decomposition of the Lewis acid-base adducts, to give products whose structure depend on the nature of the reagents.The reactions between α,β-unsaturated ortho-thienylazides and phenylboron dichloride gave 1,2-dihydro-1-phenyl-2-chloro, thieno-, or thieno-<1,2>azaborines in very good yield, via 1,6-cyclisation of the intermediate N,N-phenyldichloroborylamine resulting from a 1,2-shift of the phenyl group.New 1-phenyl-2-oxybis-(dithieno)-, and -(thieno)-<1,2>-azaborines were prepared by hydrolysis of the labile <1,2>azaborinechloro derivatives; cyclisation to give these systems involves an intramolecular electrophilic substitution which occurs regiospecificity at the α-position in the thiophene ring.Similar reactions with 2-azidobiphenyl using wider example of chloroboranes, i.e. diphenylboron chloride, phenylboron dichloride, or boron trichloride, led to <1,1'-biphenyl>-2-amine-N-phenyl or carbazole in different ratios (9.0/0.2; 8.0/2.0; 0/10).The results can be interpreted in terms of the degree of concertedness of the three steps of the rearrangement.