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Head‐to‐Head versus Head‐to‐Tail Dimerizations of Transient Silenes – The Solvent‐Dependent Regiospecifity of the Dimerization of 2‐(2‐Methoxyphenyl)‐1,1‐bis(trimethylsilyl)silene
Author(s) -
Schmohl Kathleen,
Blach Matthias,
Reinke Helmut,
Kempe Rhett,
Oehme Hartmut
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199811)1998:11<1667::aid-ejic1667>3.0.co;2-u
Subject(s) - trimethylsilyl , chemistry , silene , silylation , solvent , ether , medicinal chemistry , hydrolysis , stereochemistry , photochemistry , catalysis , organic chemistry , genetics , biology
The regiospecifity of the dimerization of the transient 2‐(2‐methoxyphenyl)‐1,1‐bis(trimethylsilyl)silene ( 6 ), synthesized by base‐initiated trimethylsilanolate elimination from (2‐methoxyphenyl)[tris(trimethylsilyl)silyl]methanol ( 5 ) according to a modified Peterson mechanism, decisively depends on the donating ability of the solvent in which the silene is generated. In ether, 6 undergoes a formal [2 + 2] dimerization to afford 3,4‐bis(2‐methoxyphenyl)‐1,1,2,2‐tetrakis(trimethylsilyl)‐1,2‐disilacyclobutane ( 12 ), whereas in toluene the head‐to‐tail [2 + 2] cyclodimer, 2,4‐bis(2‐methoxyphenyl)‐1,1,3,3‐tetrakis(trimethylsilyl)‐1,3‐disilacyclobutane ( 13 ) was obtained. 1,1‐Bis(trimethylsilyl)‐2‐(2,4,6‐trimethoxyphenyl)silene ( 18 ), similarly made by a modified Peterson reaction, under the same conditions reacted with the eliminated trimethylsilanolate with readdition at the polar Si=C bond to give, after hydrolysis, 2‐(2,4,6‐trimethoxybenzyl)‐1,1,1,3,3,3‐hexamethyl‐2‐(trimethylsiloxy)trisilane ( 19 ). A possible mechanism explaining the solvent‐dependent regiospecificity of the dimerization of 6 is discussed. The structures of 12 and 13 were determined on the basis of NMR and MS data as well as X‐ray structural analyses.