Preparation of Alkyl Silyl Acetals from Carboxylic Esters with<i>tert</i>-Butyldimethylsilyldihalomethyllithium. 1,3-Rearrangement of Silyl Group from Carbon to Oxygen
Treatment of ethyl benzoate or isopropyl formate with tert-butyldimethylsilyldibromomethyllithium gave alkyl silyl mixed acetal via 1,3-rearrangement of silylgroupfromcarbon to oxygen. The reaction of the mixed acetals with allylsilane in the presence of Lewis acid afforded allylated ethers.
tert-Butyldimethylsilyldihalomethyllithium as a dihalomethylene dianion synthon. 1,3-Rearrangement and 1,4-rearrangement of silyl group from carbon to oxide
One-pot synthesis of R1CH(OSiMe2-t-Bu)CX2CH(OH)R2 (X=Cl, Br) successive addition of two different aldehydes (R1CHO and R2CHO) has been achieved starting from tert-butyldimethylsilyldihalomethyllithium. Treatment of a THF solution of the title carbanion (X=Cl) with p-MeOC6H4CHO or n-BuCHO followed by an addition of HMPA and benzaldehyde gave the corresponding 1,3-diol monosilyl ether in 83% or 45% yield
Treatment of an ether solution of 1,1-dihalo-2-tert-butyldimethylsiloxyalkane 1 with lithium diisopropylamide at 78-degrees-C gave lithium carbenoid 2 which provided (Z)-1-halo-2-tert-butyldimethylsiloxy-1-alkene regio- and stereoselectively upon warming to room temperature.
One-pot synthesis of α,β-unsaturated ketones from tert-butyldimethylsilyldibromomethane and two different aldehydes
provided α-bromo-α-silyl ketone. Further treatment of the α-bromo-α-silyl ketone with butyllithium afforded enolate which provided β-hydroxy-α-silyl ketone upon treatment with aldehyde in ether. The enolate gave α,β-unsaturated ketone or monosilyl ether of 2-acyl-1,3-diol in THF instead of ether.