Trialkylsilanes in trifluoroacetic acid media selectively reduce the carbonyl group of arylcarbonyl compounds to methylene. Aryl alkyl ketones and diaryl ketones that can be synthesized by Friedel-Crafts acylation procedures are quantitatively reduced to the corresponding arenes.Benzaldehydes substituted with activating groups form the corresponding toluenes; however, substituted toluene formation is competitive with Friedel-Crafts alkylation. Specific -lactone formation occurs in the reduction of 3-benzoylpropanoic and o-benzoylbenzoic acids. The requirements and limitations of trialkylsilane reductions have been examined and procedures for the isolation of arene products determined.The reduction of the carbonyl group of aldehydes and ketones to methylene has enjoyed wide application in organic syntheses. Of the reductive methods that have been employed, the Clemmensen1 2 and Wolff-Kishner3 reactions have exhibited the most general utility. Other methods, including catalytic hydrogenation,4 5reductions using Raney nickel in hydroxide media,6 and trichlorosilane-trialkylamine6 and metal hydride reductions,7 have been successfully applied more specifically to aryl aldehydes and ketones.Kursanov, Parnés, and coworkers have recently reported the reduction of the carbonyl group of benzophenone, Michler's ketone, acetophenone, and 2,4,6trimethylbenzaldehyde to methylene using triethylsilane in trifluoroacetic acid media.8 *Because of the good yields reported for these silane reductions and the reported ability of silanes to undergo hydride(1) (a) Support for this work from the Research Corporation is gratefully acknowledged, (b) Part I:

phenylcarbinol, optical purity 27.2%, was recovered upon hydrolysis.(19) A control of the residual optically active 2-methylbutyl group bound to the zinc atom on the stereochemistry of the MPV reaction seems to be excluded.17 In fact, a similar result was obtained when isobutyl[(S)-1-phenyl-2,2-dimethylpropoxy]zlnc (optical purity 10.2%) was heated at 86.5" for 24 hr with an equivalent amount of fert-butyl phenyl ketone; the carbinol recovered was 7.2% optically pure. (20) See ref 6c and 7a and references cited therein.

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Am Beispiel von (I) und (II) wird die selektive Reduktion von Aldehyden und Ketonen zu Alkoholen und Äthern durch Hydrogensilane (III) in Gegenwart von Bortrifluorid‐Ätherat untersucht.

Aromatische Ketone (I) werden bei der Behandlung mit Silanen (II) in Gegenwart von Trifluoressigsäure zu den Methylenverbindungen (III) reduziert.