110472-67-8Relevant articles and documents
Reactions of Cyclobutadiene-Type Diazadiboretidines
Schreyer, Peter,Paetzold, Peter,Boese, Roland
, p. 195 - 206 (2007/10/02)
Reactions of the diazadiboretidines 2 (1a-d, R = Me, Et, Bu, tBu) with Lewis acids, protic reagents, and multiple bond systems are described.The 1:1 adducts 2b1, b2 are formed from 1b and the Lewis acids ZnCl2 and AlCl3. 1b is protolyzed by the tBuOH and tBuNH2 in a 1:1 reaction giving the open-chain products 3b1, b2.The enolysation products 4c1-c3 are isolated from the reaction of 1c with the ketones Me(R)CO (R = Me, tBu, Ph).In the presence of ZnCl2, ring opening of 1a, b is observed with 1-alkynes HCCR (R = H, tBu, Ph, COOMe), yielding the products 5a, b1-b4; both protons of HCCH can be applied, thus transforming two mol of 1b into 6b.The same alkynes are added to the sterically crowded 1d without opening of the ring; heating of the products 7d1-d3 leads to ring splitting with formation of the fragments 8d2, d3, 9d.A ring expansion of 1c to give the six-membered rings 10c1-c6 occurs on reaction with the CO groups of RCHO , (CF3)2CO, and partly Me(Ph)CO; the analogous products 10b, e1, e2 may be synthesized by the addition of Ph2C=C=O to 1b and of PhCHO to the diazadiboretidine -N(tBu)-> (1e).In a similar way the six-membered ring products 11a, b are obtained from 1a, b and (MeOOC)CC(COOMe), whereas 1d and the same alkyne give the 1:2 bicyclic adduct 12d.The central structural unit of 11a turns out to be a non-planar, twisted six-membered ring from an X-ray structure analysis.The bicyclohexene homologues 13b, d are formed from 1b, d and (EtOOC)N=N(COOEt) at ambient temperature; above 60 deg C, however, the ring expansion products 14a, b are isolated from 1a, b and the same azo compound.
