Methylenephosphine oxides

The Diels-Alder reaction of 1,2-dihydrophosphinine oxides with dienophiles, such as acetylenic derivatives and maleic acid derivatives affords 2-phosphabicyclo [2.2.2]octadiene and 2-phosphabicyclo[2.2.2]octene 2-oxides that may be regarded as the precursors of low-coordinate, methylenephosphine oxides that are useful in the phosphorylation of 0- and N-nucleophiles. It was observed that the photo-chemically induced fragmentation-related phosphorylation may follow a novel addition-elimination mechanism instead of the classical elimination-addition protocol. 

Also, methylenephosphine oxides undergo [4 +2] cycloaddition reactions with phenylbenzoylketene to give the cycloadducts 47. ... 

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