BORON NITROGEN-COMPOUNDS .123. PREPARATION AND REACTIONS OF BIS(AMINOBORYL) OXIDES

Bis(aminoboryl) oxides (=l,3,2-diboroxanes) of the general type [(CH3)2N]RBOBR[N(CH3)2] (la, R = N(CH3)2; lb, R = C2H5, 1c, R = C6H5) have been prepared by the controlled hydrolysis of (dimethylamino)chloroboranes, (CH3)2NBC1R. The compounds rearrange at elevated temperatures in an equilibrium reaction with the formation of boroxins, (RBO)3, and bis(dimethylamino)boranes, [(CH3)2N]2BR, a reaction that can also be used for the preparation of compounds of type 1. However, irreversible decomposition of 1 by organyl group migration to yield (dimethylamino)diorganylboranes, (CH3)2NBR2, and B,B′,B″-tris(dimethylamino)boroxin, [(CH3)2NBO]3, has also been observed at elevated temperatures. Transamination reactions of 1 have been utilized for the preparation of additional bis(aminoboryl) oxides, e.g., (C4HgN)(C6H5)BOB(C6H5)(NC4Hg) (2, C4H8NH = pyrrolidine), as well as for the synthesis of heterocyclic systems containing an annular BOB group, e.g., O(µ-RBNR’)2CX (4, X = O, S) from the reaction of 1 with (thio)ureas, (R′HN)2CX. The heterocycle O(µ-C2H5BNCH3)2BC2H5(3) was obtained from the reaction of 1b with C2H5B(NHCH3)2. Transamination of 1 with amides or aminoboronation reactions with isocyanates gave bicyclic systems (by intramolecular coordination) of the amidoborane, (R′CONR″)RBOBR(NR″COR′) (8), or ureidoborane, [(CH3)2NCONR′]RBOBR[NR′CON(CH3)2] (6), type, respectively. A triply bridged species containing both three- and four-coordinate boron, RB(µ-NHCH3)(µ-OBRO)(µ-NCH3CHNCH3)BR (10), was obtained from the reaction of 1c with N-methylformamide. © 1990, American Chemical Society. All rights reserved.