1445moval of water for 116 h. The benzene and excess pyrrolidine were removed by distillation, and the residue was fractionally distilled to give 1.40 g (10%) of enamine 33 .7 mm)] which contained 20% of the starting ketone (NMR): IR 1630, 1710 (residual C=O); NMR 6 0.86 (s,9 H, tert-butyl), 1.09 (d, J = 7.1 Hz, CH3CH), 4.15 (d, J = 1.5 Hz, vinyl H of major isomer), 4.41 (br s, vinyl H of minor isomer).The lower boiling fractions from the reaction mixture consisted of recovered ketone and mixtures of the ketone and enamine.ll-Methyl-14-noreudesm-4-en-3-one (34). To a solution of 0.469 g (0.0021 mol) of enamine 33 in 1.0 mL of dry methanol, under nitrogen, was added rapidly, with stirring, 0.389 g (0.0056 mol) of MVK. The reaction mixture was heated at reflux for 5 h and then hydrolyzed, and the products were isolated by the procedure described above. The combined crude products from five runs of approximately this scale using a total of 2.44 g (0.012 mol) of enamine were combined and distilled [bp 136-146 "C (air bath; 0.01 mm)] to give 0.426 g (18%) of enone 34 as a yellow oil, contaminated with 18% of the starting cyclohexanone (GLC), which was dissolved in hexanes and chromatographed on silica gel. Elution with hexanes-ether mixtures gave 0.187 g of enone 34 as a white crystalline solid which was homogeneous to GLC.Repeated crystallization from pentane at -15 "C afforded material with the following: mp 78-78.5 OC; IR 1645, 2910; NMR 6 0.90 (s, 9 H, tert-butyl), 1.21 (8, 3 H, CH3), 5.73 (8, 1 H, C=CH); mass spectrum, m/e (relative intensity) GLC analysis of the crude reaction mixture indicated that enone 34 and 2-methyl-5-tert-butylcyclohexanone were the only volatile substances present.Acknowledgment. The JEOL FX-90 Q NMR spectrometer was obtained through an NSF Support of Research Equipment grant.A synthetic route for the preparation of 5,5-dialkylcyclopentdienes (1) via 4,4-dialkylcyclopent-2-en-l-ones (3) is described. Beginning 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-didkylglutaric acids 4 and their ethyl eaters 7, masked acyloins 8, cyclopentenones 3, alcohols 9, and bromides 10 to reach the dienes 1. Physical properties of five such derivativea 1 and 3 (dimethyl, methylethyl, diethyl, methyl-n-propyl, and methylisopropyl) are presented.
IntroductionIt is possible to formulate a number of mechanistic problems which could be addressed if even small quantities
