ALKOXYCARBONYLATION REACTION INVOLVING A TANDEM 1,3-METAL SHIFT ACROSS CONJUGATED ALLYL AND ALKYNE BONDS

The reaction between CpW(CO)(3)Na and 1-chlorohex-2-en-4-yne (1; cis/trans = 1/4) gave CpW(CO)(3)(eta(1)-hex-2-en-4-yn-1-yl) (2) in good yield (cis/trans = 1/4). The cis/trans isomers of 2 were separated on a silica column at 0 degrees C. Treatment of the trans isomer 2a with TCNE gave the [3 + 2] cycloaddition product exclusively to retain the eta(1)-allyl activity. Addition of CF3SO3H (1.1 equiv) to 2a in cold diethyl ether in the presence of CH3OH gave CpW(CO)(3)(eta(1)-trans-4-oxo-2-hexen-1-yl) (5) in 61% yield. Stirring of 2a with RXH (RXH = H2O, MeOH, Me(2)CHCH(2)NH(2)) in THF over Florisil at 30 degrees C led to a new carbonylation to give CpW(CO)(2)(eta(3)-1-syn-COXR-1-anti-Me-3-syn-vinylallyl) compounds (RX = OH (6), MeO (7), Me(2)CHCH(2)NH (8)) in 52-18% yields. The reaction of CpW(CO)(3)Na and 1-chloro-8-hydroxy-2-octen-4-yne gave the corresponding eta(1)-anyl compound which on a silica column produced the intramolecular alkoxycarbonylation product 13 in moderate yield. In the presence of BF3 . Et(2)O, compound 7 reacted with aldehydes and unsaturated enones to give eta(4)-diene salts, which after demetalation by Me(3)NO liberated organic products in 40-55% isolated yields.