Cationic (R,R)-Cr(salen) complex 2 was found to catalyze enantioselective addition of 2-(trimethylsilyloxy)furan to aldehydes to give 5-substituted butenolides, though diastereoselectivity was only modest. The presence of a small amount of water is essential for achieving high enantioselectivity.
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Matsuoka et al. (2003) studied this question.