Alkyl Enol Ethers Research Articles

Trityl Salts Catalyzed Aldol-Type Reaction of Alkyl Enol Ethers with Acetals

Abstract β-Alkoxy ketones are synthesized in good yields by the reaction of alkyl enol ethers with acetals in the presence of a catalytic amount of trityl salts. Of enol ethers, methoxymethyl (MOM) enol ether exhibits an enhanced reactivity as a nucleophile.

Synthesis of Furan Derivatives. XLV. A New Acid catalyzed Cyclization of sterically Hindered cis Alkenals

Preparation of aryl 2, 4-dialkyl-2, 4-pentadienals (aryl is (5-nitro-2-furyl)- or (5-nitro-2-thienyl)-, alkyl is methyl or ethyl) by condensation of alkyl enol ether R-CH=CH-OR R〓H) with aryl-α-alkylated acrolein acetals gave stereoselectively 2-cis-4-trans-2, 4-dialkylated pentadienals. Driving force leading to above configuration is overcrawding control of the sterically hindered chain. The stereoselective formation of cis-alkenals was found to be applicable for aryl 2-cis-4-cis-6-trans-trialkylated heptatrienal. All hindered cis alkenals prepared in this paper cyclized to five or seven membered cyclic ketones in the presence of HCl or some organic acids. A mechanism for the cyclization was proposed, that involves initial formation of oxocarbonium ion, which is later transformed by two of successive processes, i.e., the formation of bicyclo-[2.1.0] cyclopentanone derivative and its ring rupture by acid. Proposed mechanism was discussed from the result of deuterohydrochloric acid incorporated cyclization of IVa.