| Abstract
| - Pd(OAc)2 combined with nitrogen-containing ligands (e.g., 2,2‘-bipyridine) catalyzed the cyclizationof (Z)-4‘-acetoxy-2‘-butenyl 2-alkynoates (1) in acetic acid to afford the α-(Z)-acetoxyalkylidene-β-vinyl-γ-butyrolactones (2) with high efficiency and high stereoselectivity. The nitrogen-containingligands, like halides, served to favor β-heteroatom elimination over β-hydride elimination inPd(II)-mediated reactions. The generality of this ligand effect was probed in both stoichiometricand catalytic reactions. With these results in hand, the catalytic asymmetric protocol was achievedwith high enantioselectivity (up to 92% ee) when pymox (pyridyl monooxazoline) or bisoxazolinewas used. The absolute configuration of the products and the synthetic utility of this asymmetrictransformation were established through the convenient synthesis of (3S)-(+)-A-factor.
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