Diazo phosphonates as useful synthetic intermediates for total synthesis

A series of acceptor-acceptor type diazo phosphonates were successfully synthesized. When exposed to Rh2(OAc)4, depending on their substitution patterns, vinyl diazo phosphonates underwent either sulfonium ylide rearrangements or C-H insertion reactions to provide C-3 quaternary indolines or cyclopentenes, respectively. Diazo vinyl phosphonates, on the other hand, reacted with alcohols, amines and thiols in the presence of a Rh catalyst to generate vinyl ethers, enamines and vinyl sulfides. Intramolecular cyclization of the resulting vinyl ethers led to the formation of oxetanes and furans. This O-H insertion/ intramolecular cyclization strategy was utilized in the synthesis of the phosphonate analog of dysiherbaine.