Geminate-Substituted Cyclopentadienes. 1. Synthesis of 5,5-Dialkylcyclopentadienes via 4,4-Dialkylcyclopent-2-en-1-ones.

Article abstract of DOI:10.1021/jo00347a013

A synthetic route for the preparation of 5,5,-dialkylcyclopentadienes (1) via 4,4-dialkylcyclopent-2-en-1-ones (3) is described.Beginnig with ketones (in which the two carbonyl substituents will become the two alkyl groups in the title compounds), the route traverses the Guareschi imides 5, 3,3-dialkylglutaric acids 4 and their ethyl esters 7, masked acyloins 8, cyclopentenones 3, alkohols 9, and bromides 10 to reach the dienes 1.Physical properties of five such derivates 1 and 3 (dimethyl, methylethyl,diethyl, methyl-n-propyl, and methylisopropyl) are presented.