F- Induced Oxidative Cleavage of Phenyldimethylsilyl Groups

To a solution of (RR,55)-2-me thy l-3-pheny Idimet hylsily 1-3-phenyl-propionic acid (50 mmol) (see Chapter 8) in dichloromethane (50ml), 

The fluorosilane was dissolved with stirring in peracetic acid (72 ml, 40% solution in AcOH) at 0°C. Triethylamine (53 mmol) was added dropwise, and the mixture was allowed to come to ambient temperature. After being stirred at ambient temperature for 3.25 h, the mixture was poured into aqueous KOH (250 ml, 2 m), and the pH was brought to 11 by the addition of solid KOH pellets. The resulting mixture was extracted with ether (2x100 ml), and the aqueous phase was carefully acidified with concentrated sulphuric acid to pH 1. This acidified phase was then extracted with ether (4 x 100 ml), and the combined organic extracts were dried. Concentration in vacuo and crystallization (pentane acetone, 3 1) gave the/3-hydroxy acid (44.5 mmol, 89%), m.p. 92-94°C. 

For earlier work on this process, see R. Muller. Z. Chem. 24, 41 (1984) E. Bunccl and A. G. Davies, J. Chem. Soc. 1550 (1958). See also E. W. Colvin, Oxidation of Carbon-Silicon bonds, Vol. 7, Comprehensive Organic Synthesis, ed. B. M. Trost and I. Fleming. Chapter 4.3. Pergamon. Oxford (1990) in press. 

Parker, Ph.D. thesis, Cambridge University (1985) I. Fleming, personal communication 1. Fleming and P. E. J. Sanderson. Tetrahedron Lett. 28,4229 (1987) for a recent example of use. see W. Oppolzer. R. J. Mills. W. Pachinger and T. Stevenson. Helv. Chim. Acta 69, 1542(1986). 

Reaction between TMSCH2MgCl and n-octanal in refluxing THF, followed by isolation by pouring on to ice and saturated ammonium chloride solution and normal extractive procedures gave 2-hydroxynonyltrimethylsilane, b.p. 82-83 °C/1 mmHg. 

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