Organolead-mediated arylation of allyl β-ketoesters: a selective synthesis of isoflavanones and isoflavones

Abstract

Arylation of A-ring substituted and unsubstituted 3-allyloxycarbonylchroman-4-ones with aryllead (iv) triacetates followed b y selective catalytic deal lyloxycarbonylation affords isof lavanones or isof lavones in high overall yields. The highest yield in the arylation step was observed in the reaction of 5,7dimethoxychroman-4-one with the more hindered 2,4,6-trimethoxyphenyllead triacetate.

Asymmetric Synthesis of the β-Methyl-Substituted Analogues of (+)-Tanikolide and (–)-Malyngolide

“…Tris(dibenzylideneacetone)dipalladium(0) chloroform adduct was prepared via the method of Zalesskiy et al [55]. Allyl cyanoformate was prepared via a previously reported method [56]. Magnesium turnings were activated at 80°C under high vacuum for 1 h prior to use.…”

Synthesis of Isoflavones

“…Arylation of 3-(allyloxycarbonyl)-4-chromanones 2 4 has also been utilized for the preparation of isoflavones 6 [174][175][176][177]. An organobismuth-mediated coupling reaction was used for this purpose, but the utility of this method is strongly limited by the difficult availability of the arylbismuth(V) reagent [174].…”

“…An organobismuth-mediated coupling reaction was used for this purpose, but the utility of this method is strongly limited by the difficult availability of the arylbismuth(V) reagent [174]. Aryllead(IV) triacetate proved to be a convenient reagent providing isoflavanones 25 which yielded isoflavones 6 on oxidation with catalytic amounts of palladium(II) acetate and 1,2-bis(diphenylphosphino)ethane (DPPE) in acetonitrile (Scheme 16) [175,176].…”

Enantioselective Synthesis of a Polyfunctionalized Tetracycle Related to Pentacyclic Triterpenes by Using an Anionic Cycloaddition Reaction

“…The OH group of 13 was then protected as a benzyl ether with benzyl trichloroethanimidate [9]. The resulting enone 14 was then kinetically deprotonated with LiHMDS and added on allyl carbonocyanidate [10] to afford b-keto ester 6 in 24% overall yield in five steps starting from 12.…”