Novel [2+2] cycloaddition reactions of (dimethylamino)bis(trifluoromethyl)borane, (CF3)(2)BNMe2, with N-sulfinylsulfonamides, aminoiminophosphines, carbodiimides, and a keteneimine

(Dimethylamino)bis(trifluoromethyl)borane (CF3)(2)BNMe2 (1), combines with N-sulfinylsulfonamides R-O2S-N=S=O in a [2 + 2] fashion to form (CF3)(2)B-NMe2-S(O)-N-SO2R (R = Me (2a), Et (2b), iPr (2c), Ph (2d), and pTol(2e)). Aminoiminophosphines RN=P-NR2' react with 1 analogously to yield the heterocycles (CF3)(2)B-NMe2-P(NR2')-NR (R = SiMe3, NR2' = N(SiMe3)(2) (3a), TMP (3b); R = tBu, NR2' = N(SiMe3)tBu (3c), NiPr2 (3d), TMP (3e)). Carbodiimides R-N=C=N-R add to the B=N bond of 1 to give unstable adducts (CF3)(2)B-NMe2-C(NR)-NR which rearrange at 20 degrees C to yield the four-membered heterocycles (CF3)(2)B-NR-C(NMe2)-NR (R = iPr (5a), cC(6)H(11) (5b)) For carbodiimides with aryl substituents R = pXC(6)H(4), this rearrangement competes with an internal electrophilic aromatic substitution reaction and mixtures of the two isomers (CF3)(2)B-NC6H4X-C(NMe2)-NC6H4X (X = H (5c), Me (5d), OMe (5e)) and (CF3)(2)B-CCHCXCHCHC-NH-C(NMe2)-N-(C6H4X) (X = H (6c), Me (6d), OMe (6e)) are obtained. Ph-N=C=CMe2 combines with 1 to form the four-membered ring (CF3)2B-CMe2-C(NMe2)-NPh (8). F3C-CH2-N=S=O undergoes an ene-type reaction with 1 by which the dimethylamine borane (F3C-HC=N-S(=O))(CF3)(2)B . NHMe2 (9) is formed. The constitution of the novel boron compounds has been deduced from multinuclear NMR, In, and mass spectra. The structures of 2a, 3c, 5c, 6d, 6e, and 8 have been investigated by single-crystal X-ray diffraction.