PHOSPHONOPYRUVATES - SYNTHESES, NMR INVESTIGATIONS, AND REACTIONS

The new 3-(diethoxyphosphoryl)-2-oxopropanoates 5-24 and -propanamides 25-38 with various substituents at C(3) were prepared in moderate-to-good yields (Schemes 2 and 3, Tables 1 and 2). It was shown that they adopt a preferred conformation in which the diethoxyphosphoryl group and the substituent at C(4) are antiperiplanar to each other (see B). The keto-enol tautomerization of phosphonopyruvates with Ph-C(3) (see 20) and MeS-C(3) (see 24 and 33) was examined. In CHCl3, two tautomeric species exist, whereas in dimethylsulfoxide (DMSO), three tautomeric forms are observed. Grime ethers, an oxime, and a phenylhydrazone of unsubstituted phosphonopyruvates were prepared (see 40-44), and quinoxalin-2(1H)-ones could be obtained from the reaction of pyruvates with 4,5-dimethylbenzene-1,2-diamine (see 45-47).