Syntheses of [6,6]-Fused-Ring 1,2-Azaborines

BN-naphthalene
(2) and BN-tetralin (7) have been prepared
by a short synthesis from allyltributylstannane
(3). The reaction of 3 with BCl3 followed by diallylamine and Et3N afforded (diallylamino)­diallylborane
(5), which gave 1,4,5,8-tetrahydro­[1,2]­azaborino­[1,2-a]­[1,2]­azaborine (6), on treatment with
Grubbs (I) catalyst. The reaction of 6 with Pd gave 2 and 7. The reaction of 7 with
Cr­(CO)6 gave the corresponding Cr­(CO)3 adduct 8, for which a crystal structure has been obtained. The isomerization
of 6 to 7 has been examined using DFT calculations.