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1.2.3.5.3 Intramolecular Addition of Malonate Derivatives to Alkynes under Strongly Basic Conditions: Four Modes of Reaction

DOI: 10.1055/sos-SD-001-00206

Takacs, J. M.; Vayalakkada, S.; Jiang, X.Science of Synthesis, (20011302.

The intramolecular palladium-catalyzed reaction of certain alkynylmalonate derivatives (e.g., 152) follows an unusual course when the reaction is carried out in the presence of stoichiometric potassium tert-butoxide (Scheme 42).[‌36‌] In the presence of catalytic potassium tert-butoxide, 152 undergoes cyclization, proceeding as described in Sections 1.2.3.5.1 and 1.2.3.5.2 to afford methylenecyclopentane 154 in good yield. These particular reactions are carried out in tetrahydrofuran using what is suggested to be 5mol% Pd(0)(dppe) as the catalyst, generated in situ via the reduction of palladium(II) acetate by hept-1-ene. In the presence of stoichiometric potassium tert-butoxide the reaction follows a different course, with selective loss of one of the carbanion stabilizing groups, to afford the cyclopentene derivative 153 in good yield.

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