Horner-Wadsworth-Emmons reactions, dimethyl

Reactions of lithiated dimethyl cyclohex-2-enylphosphonate (775) with aldehydes were studied and determined to proceed with a or 6 regio-selectivity. Such an unusual regioselectivity resulted from the contribution of two allylic carbanions one, stabilised by the phosphonate moiety and the other stabilised by the carboethoxy group. The products of the Horner-Wadsworth-Emmons reaction, including an analogue of some retinol metabolites (776), were formed under kinetic conditions whereas the 5-adduct (774) with benzaldehyde was obtained as a thermodynamic product (Scheme 197). °... 

Shibasaki made several improvements in the asymmetric Michael addition reaction using the previously developed BINOL-based (R)-ALB, (R)-6, and (R)-LPB, (R)-7 [1]. The former is prepared from (R)-BINOL, diisobutylaluminum hydride, and butyllithium, while the latter is from (R)-BINOL, La(Oz -Pr)3, and potassium f-butoxide. Only 0.1 mol % of (R)-6 and 0.09 mol % of potassium f-butoxide were needed to catalyze the addition of dimethyl malonate to 2-cy-clohexenone on a kilogram scale in >99% ee, when 4-A molecular sieves were added [15,16]. (R)-6 in the presence of sodium f-butoxide catalyzes the asymmetric 1,4-addition of the Horner-Wadsworth-Emmons reagent [17]. (R)-7 catalyzes the addition of nitromethane to chalcone [18]. Feringa prepared another aluminum complex from BINOL and lithium aluminum hydride and used this in the addition of nitroacetate to methyl vinyl ketone [19]. Later, Shibasaki developed a linked lanthanum reagent (R,R)-8 for the same asymmetric addition, in which two BINOLs were connected at the 3-positions with a 2-oxapropylene... 

The conjugate base of dimethyl methylphosphonate readily reacts with alcohols and carbonyl compounds in the gas phase. (Me0)2P(0) CH2" reacts with CD3OH via three pathways, each of which proceed initially via proton transfer to form the ion-molecule complex [CD3O" (Me0)2P(0)Me], which subsequently undergoes S 2 attack at carbon (equation 56a) or addition/elimination at phosphorus (equation 56b and c). (MeO)2 P(0)CH2 reacts with methyl pyruvate via proton transfer (equation 57a), addition/ elimination (equation 57b) and also via a Horner-Emmons-Wadsworth reaction (equation 57c). The latter reaction is the dominant one for benzaldehyde. Although a consideration of the reactions of phosphate esters were not a mandate for this review, it is... 

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