Methyl-3-phenylprop-2-enal

This provides a route to a/9-unsaturated aldehydes (25). 2-Methyl-3-phenylprop-2-enal (25) 

A solution of the trimethylsilyl enol ether of propionyl trimethylsilane (5 mmol) (Chapter 12) and benzaldehyde diethyl acetal (5 mmol) in dichloromethane (10 ml) was added to a solution of BF3.OEt2 (5 mmol) in dichloromethane (5 ml), cooled to —78°C. After being stirred for lh at -78°C and 2h at -30°C, the mixture was quenched with excess saturated sodium hydrogen carbonate solution, and extracted with ether. Concentration and distillation gave the product /3-ethoxy acylsilane, (4.6mmol, 95%), b.p. 105-106°C/2mmHg. Treatment of this alkoxy 

(a) With acetals, the product unsaturated aldehydes are usually exclusively ( ). 

Lewis-acid-induced alkylation reactions, employing SN1 electrophiles, has been advanced and reviewed by Reetz (26) and Fleming (27) and their collaborators. 

TMSOTf-catalysed reaction with dimethyl acetals 

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Methoxytrimethylsilane, 123 Methyl acetoacetate, 92 Methyl bromoacetate, 107 Methyl 11-hydroxyundecanoate, 58 Methyl lithium, 27,28 Methyl 10-undecenoatc, 58 2-MethyM,3-dithiane, 81 (V f ,55)-Methyl-3-phenyldimethyl-silyl-3-phenylpropionic acid. 53-4 2-Methyl-3-Phenylprop-2-enal, 111 2-Methyl-2-trimethylsilyl-l,3-dithiane, 81 2-Methyl-l-(trimethylsilyloxy)cydo-hex-l-ene, 100,109 2-Methyl-l-trimethylsilyloxy-cyclo-hex-6-ene, 100... 

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