A new and general method for preparing Fischer-type alkoxycarbene complexes 1 is reported. This method involves the alkylation of acylate complexes 7 with alkyldiphenylsulfonium salts 10 with a variety of functionalized alkyl groups. The alkylation of tetramethylammonium pentacarbonyl(1-oxyalkylidene)chromate(0) 7a-c, tetramethylammonium pentacarbonyl(1-oxymethylidene)molybdate(0) 7d, and pentacarbonyl(1-oxymethylidene)tungstate(0) 7e with alkyldiphenylsulfonium salts 10 proceeded smoothly under mild conditions to give the corresponding alkoxycarbene complexes 12-39 in good to high yields. Competitive alkylation of 7a with methyl-11 and isopropyldiphenylsulfonium tetrafluoroborate 40 shows a higher reactivity of the isopropyl group, suggesting the participation of an S-O sulfurane intermediate 41.
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