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26.1.9.9 Method 9: Alkylation by Phase-Transfer Catalysis

DOI: 10.1055/sos-SD-026-00361

Plaquevent, J.-C.; Cahard, D.; Guillen, F.Science of Synthesis, (200526487.

Alkylation by phase-transfer catalysis represents a very attractive method in synthetic chemistry, since it requires mild conditions and uses inexpensive reagents and solvents; in some cases, solvent is not needed at all.

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In 1984, the first enantioselective alkylation of a ketone (e.g., 37) via its enolate with chloromethane under phase-transfer catalysis conditions using chiral cinchoninium cation 36 was reported.[‌79‌] The resulting enantiomerically enriched ketone (S)-38 (92% ee) is transformed into (+)-indacrinone in several steps (Scheme 24). This very important result stimulated further studies in asymmetric phase-transfer catalysis, the more exciting results having been published in the field of aminoacid chemistry.[‌80‌] The mechanistic studies of this reaction produced a number of significant findings.[‌81‌]

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