Tol-BINAP-CuF

A recent synthesis of P-D lactone (Scheme 13.51) used an enantioselective catalytic approach. A conjugate addition of a silyl ketene acetal derived from an unsaturated ester gave an unsaturated lactone intermediate. The catalyst is CuF-(S )-tol-BINAP.30 The catalytic cycle for the reaction is shown below. 

Table 8 Aldolizations of unsaturated aldehydes using CuF(S)-Tol-BINAP as the catalyst...

Scheme 10 Proposed catalytic cycle of the CuF-Tol-BINAP catalysis...

The Tol-BINAP complexes of CuFa, CuF, and CuOt-Bu also work as efficient chiral catalysts of the aldol reactions of aromatic and a, -unsaturated aldehydes wifh dienolate 64 (Scheme 10.62) [164]. IR spectroscopy has revealed fhat the stoichiometric reaction of 64 wifh Cu(Ot-Bu)(S)-Tol-BINAP forms a Cu(I) enolate, and fhat subsequent reaction wifh an aldehyde gives a copper aldolate. The copper enolate is also obtained by stepwise treatment of 64 with Bu4NPh3SiF2 and Cu(C1O4)(S)-To1-BINAP. These results, with the known reduction of Cu(II) to Cu(I) by SEE, indicate that fhe Cu-catalyzed aldol reactions proceed fhrough a transmetalation mechanism involving a chiral Cu(I) enolate. 

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