Cyclopropan‐Derivate, 2. Selbst‐Acylierung der α‐Alkyl‐γ‐lactone zu Herstellung von Bis(1‐alkylcyclopropyl)ketonen über Spiro[4.4]acetale

Cyclopropane Derivatives, 2. — Self‐Acylation of α‐Alkyl‐γ‐lactones To Give Bis(1‐alkylcyclopropyl)ketones via Spiro[4.4]acetals High‐yield synthetic ways are recommended for the title lactones 1 .The coupling of two 2‐alkyl‐4‐butanolides is possible in an inter‐( 1b, c ) or intramolecular fashion ( 4c ) to give spiro[4.4] acetals 8 or 9 respectively, in the absence of hindering substituents. Symmetrically substituted bis(1‐alkylcyclopropyl)ketones 12 and 13 may be prepared by acidic cleavage of those spiro[4.4] acetals lacking 2,7‐substituent.