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Two plus two plus two: An enantioselective synthesis of P-stereogenic alkynylphosphine oxides through a cationic rhodium(I)/modified-binap complex catalyzed 2+2+2 cycloaddition of symmetrical dialkynylphosphine oxides with 1,6-diynes was developed (see scheme; binap=2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl, Z=CH2, O, or N-sulfonamide). Furthermore, this method permits the synthesis of a C2-symmetric P-stereogenic bis(alkynylphosphine oxide).
Nishida et al. (2008) studied this question.