A New Synthesis of Polyquinanes Utilizing alpha-Ketovinylphosphonates

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This project is composed of three subjects as mentioned below. (1) Convenient Synthesis of Functionalized CyclopentanoidsA new approach to cyclopentane annulated compounds was successfully achieved by using 1-(cyclopent-1-enylcarbonyl)vinylphosphonates 1, which we newly developed. Treatment of 1 with Lewis acids or polyphosphoric acid led to 2-phosphorylcyclopentenone annulated compounds in 25-71% yields. The Michael addition of (1,3-dioxolan-2-yl)ethylmagnesium bromide to 1, followed by acidic hydrolysis and the intramolecular Wittig-Horner reaction gave divinyl ketones 2 (51-70%). Nazarov cyclization of 2 produced cyclopentane annulated compounds 3 in good yields. (2) Arylation of Phosphonate Carbanions and Synthetic Application of alpha-ArylmethylphosphonatesCopper(I)-catalyzed reaction of phosphonate carbanions with aryliodides in DMF gave alpha-arylated phosphonates in good yields. Functionalized dihydroisoquinoline N-oxides and N-phenyl(or alkyl) imines were synthesized from alpha-(o-formylphenyl)methyl-phosphonates prepared, paraformaldehyde, and oxime or hydrazines. 1,3-Dipolar cycloaddition of the 1,3-dipoles to dipolarophiles gave the cycloadducts. (3) Synthesis of Cyclic Terpenoids via Intramolecular Ene Reaction of VinylphosphonatesLewis acid promoted intramolecular ene reaction of the vinylphosphonates, prepared from citronellal or 2,6-dimethyl-5-heptenal and triethyl phosphonoacetate, gave stereoselectively cyclic terpenoids bearing the phosphono group in good yields. The wittig reaction of the terpenoids with paraformaldehyde, followed by intramolecular ene reaction provided the bicyclic terpenoids in good to moderate yields.