Enantioselective Intramolecular [2+2+2] Cycloaddition of Dienynes for the Construction of Adjacent Three Chiral Centers

Abstract

A chiral rhodium catalyst realized the first intramolecular [2+2+2] cycloaddition of yne-ene-enes, and chiral multicyclic cyclohexenes with adjacent three chiral centers were afforded with high to excellent ee.

Key words

catalysis - chirality - cycloaddition - rhodium - multi­cyclic

Reference and Notes

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14

The counter anion of the Rh catalyst did not affect the yield of 2a and its ee (BF₄: 74%, 87% ee, OTf: 69%, 86% ee).

15

The ene-type products and their isomerized products were also formed in each entry.

16

The reaction of carbon-tethered dienyne 1f did not proceeded even at 80 ˚C. Oxygen-tethered dienyne 1g was promptly consumed at r.t. but ene-type products were formed and no cycloadduct could be detected.

17

Based on Scheme  [²] , the absolute configuration of the tricyclic product would be determined at the formation of the bicyclic metallacyclopentene, which is the same interme-diate as that of [2+2+2] cycloaddition of enediynes, see ref. 7a.