The Iminoborane t BuB≡N t Bu as a Dipolarphile in (2+3) Cycloadditions

The iminoborane t BuB≡N t Bu and the diazomethane t BuCH=N 2 give the (2+3) cycloadduct [—HC(tBu)—N=N—N(tBu)=B(tBu)—] in a 1:1 reaction and the seven‐membered ring [—C( t Bu)=N—NH—N( t Bu)=B( t Bu)—N( t Bu)=B( t Bu)—] in a 2:1 reaction. The (2+3) cycloadduct decomposes above 0 °C to give the seven‐membered ring, N 2 , and HC( t Bu)=N—N=CH( t Bu) in the ratio 2:1:1. The borane t BuB≡N t Bu and organic azides R″N 3 yield the (2+3) cycloadducts [—R″N—N=N—N( t Bu)=B( t Bu)—] (R″ = Me, Et, Pr, Bu, i Bu, s Bu, C 5 H 11 , c ‐C 5 H 9 , c ‐C 6 H 11 , Bzl, EtOOC).