We have established that a cationic rhodium(I)/H8-binap complex catalyzes [2+2+2] cycloaddns. of a variety of 1,6- and 1,7-diynes with both electron-deficient and electron-rich carbonyl compds., leading to dienones in high yield under mild reaction conditions. In the reactions with acyl phosphonates, the reactivity of 1,6- and 1,7-diynes was highly dependent on their own structures. The addn. of chelating di-Et oxalate effectively promoted the [2+2+2] cycloaddns. involving acyl phosphonates, presumably due to the equil. formation of the desired 1:1 rhodium complex of the diyne and the acyl phosphonate by facile ligand exchange between the diyne and weakly coordinated di-Et oxalate. In the reactions involving bifunctional carbonyl compds. or unsym. 1,6-diynes, high chemo- or regioselectivities were obsd.(ﾂｩ Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009). [on SciFinder(R)]
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