S.E. Denmark, Z. Wang / Journal of Organometallic Chemistry 624 (2001) 372–375
375
of aryl and alkenyl iodides under mild condition in the
presence of TBAF (two equivalents) and Pd(dba)2. In
view of the mildness and generality of the transforma-
tion along with the cost and non-toxic nature of the
silicon reagents and byproducts, this procedure should
become the reaction of choice for large scale and labo-
ratory preparations. Studies on the use of in-situ gener-
ated siloxanes for cross-coupling reactions are in
progress.
rotary evaporation and vacuum drying to give the
crude product which was purified by silica gel chro-
matography (24×155 mm, hexane–ethyl acetate, 40:1)
to afford 6 as a white solid 233 mg (80%).
Acknowledgements
We gratefully acknowledge the National Science
Foundation for financial support (NSF CHE-9800398).
4. Experimental
References
A representative procedure for the cross-coupling of
1 with 5 follows. To a solution of 1 (207 mg, 0.6 mmol,
1.2 equivalents) in THF (0.2 ml) was added a solution
of TBAF (Fluka, 1 M in THF, 4.0 ml). After 10 min,
4-iodoacetophenone (5) (492 mg, 2.0 mmol) and
Pd(dba)2 (58 mg, 0.10 mmol, 5 mol%) were added
sequentially. A strong exotherm was observed (the tem-
perature of reaction solution increased from 24 to 55°C
within 6 min). After 10 min, GC analysis showed that
the iodide was consumed (HP-5, 200°C, 15 psi: tR 6,
5.40 min). Diethyl ether (10 ml) was added and the
mixture was stirred for an additional 5 min. The mix-
ture was filtered though a short column of silica gel,
which was further eluted with ether (50 ml). The com-
bined eluate was concentrated by rotary evaporation
and vacuum drying to give the crude product which
was purified by silica gel chromatography (24×162
mm, pentane–ethyl acetate, 40:1) to afford 6 as a white
solid 258 mg (88%). Spectroscopic and analytical data
matched those reported in the literature [3c].
Procedure II for the cross-coupling of 1 with 5: to a
solution of 1 (207 mg, 0.6 mmol) in THF (0.2 ml) was
added a solution of TBAF (Fluka, 1 M in THF, 4.0
ml). After 10 min, Pd(dba)2 (58 mg, 0.10 mmol, 5
mol%) was added. Then a solution of 5 in THF (2.0 ml,
1.0 M) was slowly added by syringe such that the
reaction temperature did not exceed 30°C (45 min).
After complete addition of 5, the reaction mixture was
stirred at room temperature for 10 min, whereupon GC
analysis showed that the iodide was consumed. Ether
(10 ml) was added and the mixture was stirred for an
additional 5 min. The mixture was filtered though a
short column of silica gel, then was eluted with ether
(50 ml). The combined eluate was concentrated by
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[10] 1,3,5,7-Tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (DV4 , 1,
US$0.76 per g), 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane
(DV3 , 2, US$4.60 per g), tris(vinyldimethylsiloxy)methylsilane (3,
US$3.30 per g) and hexavinyldisiloxane (4, US$5.30 per g)
purchased from Gelest were used directly without any further
purification.
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