Method for making phosphinic acid intermediates

A method for preparing a phosphinic acid intermediate of the structure ##STR30## wherein R is H or lower alkyl;

• R.sup.1 is lower alkyl, aryl, arylalkyl, cycloalkyl, or cycloalkylalkyl;
• R.sup.2, R.sup.3 and R.sup.4 are the same or different and each is independently H, lower alkyl or aryl;
• Z is --CO.sub.2 R.sup.5 (wherein R.sup.5 is H or lower alkyl), ##STR31## (wherein R.sup.6 is H, lower alkyl, aryl or arylalkyl), --CN, or ##STR32## wherein R.sup.7 and R.sup.8 are the same or different and are selected from the group consisting of H, lower alkyl, aryl, aryl-lower alkyl, cycloalkyl or cycloalkylalkyl and at least one of R.sup.7 and R.sup.8 is other than H, or R.sup.7 and R.sup.8 can be taken together with N to form a 5-, 6- or 7-membered heterocyclic ring ##STR33## which may or may not include a COOR.sup.5 substituent, which 5- or 6-membered N-containing ring may or may not be fused to an aryl ring, and
• which comprises reacting a phosphonous acid or ester thereof of the structure ##STR34## wherein R and R.sup.1 are as defined above with a conjugated compound of the structure ##STR35## wherein R.sup.2, R.sup.3, R.sup.4 and Z are as defined above, employing a molar ratio of phosphonous acid or ester thereof to the conjugated compound of within the range of from about 0.5:1 to about 10:1, in the presence of a silylating agent employing a molar ratio of phosphonous acid or ester to silylating agent of within the range of from about 0.06:1 to about 2:1 and in the presence of an inert organic solvent to form the phosphinic acid intermediate and separating the phosphinic acid intermediate from the reaction mixture.