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Reactions of boranes with aromatic azides

1985; Elsevier BV; Volume: 293; Issue: 3 Linguagem: Inglês

10.1016/0022-328x(85)80299-0

1872-8561

Paolo Zanirato,

Organoboron and organosilicon chemistry

Some halogeno(organyl)boranes have been formed to promote fragmentation of organic azides, through decomposition of the Lewis acid-base adducts, to give products whose structures 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[b]-, or thieno[c]-[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 (9.80.2; 8.02.0; 010). The results can be interpreted in terms of the degree of concertedness of the three steps of the rearrangement.