Silyl Nitronates in Organic Synthesis. Routes to Heterocycles and Cyclopentanoids. Synthesis of Allethrolone and Calythrone. Acylation and Cyanohydroxylation of Double Bonds. An Exploratory Study.
Silyl nitronates are versatile reagents for the preparation of heterocycles by dipolar addition to double bonds. The intermediate isoxazolidines [muscimol analogs] can be transformed to 2-isoxazolines, isoxazoles, furans, dihydrofuranones, pyrazoles, pyridazines and pyridazones. Reduction of 2-isoxazolines with Ti3+ led to hydroxylated 1,4-diketones which subsequently were cyclized to cyclopentenones. Routes to calythrone, rethrolones, prostanoids and a number of naturally occurring dihydrofuranones are devised, as well as synthetic procedures for acylation, preparation of endiones, hydroxyacylation, cyanation and hydroxycyanation of double bonds.