NEW MASKED DELTA-LITHIOCARBONYL COMPOUNDS - PREPARATION AND SYNTHETIC APPLICATIONS

The reaction of 2-(4-chlorobutyl)-1,3-dioxolanes (1a-c) or 2-(4-chlorobutyl)-2-ethyl-1,3-dithiane (1d) with n excess of lithium powder and a catalytic amount of naphthalene (8 mol %) in THF at -78-degrees-C leads to a solution of the corresponding masked lithium delta-enolates 2, which react with different electrophiles (water, deuterium oxide, carbonyl compounds, carboxylic acid derivatives, dibenzyl disulfide or benzylideneaniline) to yield the expected products 3-15. In the presence of a catalytic amount of CuBr.Me2S the intermediate 2a reacts with cyclohex-2-enone giving the compound 16a through a conjugate addition. The deprotection of compounds 10a, 12a, 16a and 4b-6b with 2 N HCl gives the expected functionalized carbonyl compounds 17a- 19a and 20b-22b, respectively. Finally, using silicon reagents it is possible to prepare alcohols 20a-25a, dienic alcohols 26a-29a and cyanooxepanes 30a-33a from the in situ generated hydroxyaldehydes of the type 17a with triethylsilane, allyltrimethylsilane and trimethylsilyl cyanide, respectively.