The clemmensen reduction of enol ethers: cyclopropyl ethers from mono- and di-methoxycyclohexa-1,4-dienes

✍ Scribed by Irène Elphimoff-Felkin; Pierre Sarda

• Publisher: Elsevier Science
• Year: 1983
• Tongue: French
• Weight: 213 KB
• Volume: 24
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)85915-8

✦ Synopsis

Clemmensen reduction (zinc and hydrogen chloride in dry diethyl ether) of 1-methoxy-and l,S-dimethoxy-cyclohexa-1,4-diene affords the cyclopropyl ethers, l-methoxy-and 1,5-dimethoxy-bicycloI3.l.Olhexane; in the presence of acetic anhydride, reduction of 6-acetyl-l-methoxy-6-methyl-cyclohexa-1,4-diene leads regiospecifically to 7-acetoxy-l-methoxy-6,7-dimethyl-bicyclo~4.l.O~hept-4-ene. The Clemmensen reduction (amalgamated zinc and hydrogen chloride) of a,Bunsaturated ketones and of 1,3-diketones often leads to rearranged products. The reaction has been shown to involve intermediate cyclisation to cyclopropanols or cyclopropane-diols, and a number of these have been trapped as their acetates by carrying out the reaction in the presence of acetic anhydride." ' Some typical examples are shown in Scheme 1; whereas the a,B-6oH ":-o_O' &OH b_c Scheme 1