Published in:
European Journal of Inorganic Chemistry, 2013 (2013) 14, Seite 2608-2614
Language:
English
DOI:
10.1002/ejic.201201489
ISSN:
1434-1948;
1099-0682
Origination:
Footnote:
Description:
AbstractReactions of equimolar amounts of dicyclohexylborane (DCB) with a series of 2‐alkynyl‐1,3‐diethyl‐1,3,2‐benzodiazaboroles R–C≡C–B(NEt)2C6H4 (1: R = nBu, 2: R = tBu, 3: R = Ph, 4: R = p‐Me2NC6H4, 5: R = p‐MeOC6H4) regioselectively afforded the 1,1‐diborylalkenes (Z)‐R(H)C=C{(B{NEt}2C6H4)B(c‐C6H11)2} (7a–11a) as the result of a cis‐addition of the BH bond of the borane to the C≡C triple bond in compounds 1 to 5. In contrast to this, reaction of Me3Si–C≡C–B(NEt)2C6H4 (6) with HB(c‐C6H11)2 yielded a 2.5:1 mixture of the 1,2‐diborylated alkene (Z)‐Me3Si{(c‐C6H11)2B}C=CHB(NEt)2C6H4 (12b) and the 1,1‐regioisomer (Z)‐Me3Si(H)C=C{B(NEt)2C6H4}{B(c‐C6H11)2} (12a). These results were rationalized by the differing π‐acceptor qualities of the benzodiazaborolyl and trimethylsilyl substituents at the C≡C triple bond in compounds 1 to 6. The novel products 7–12 were characterized by elemental analysis, mass spectrometry and NMR spectroscopy (1H, 11B, and 13C NMR). The molecular structures of 9b and 12b were substantiated by single‐crystal X‐ray diffraction analysis.