New Successive Reactions Utilizing Functional Carbanions

点击翻译按钮获取中文摘要

Ynolates are ketene anion equivalens, so that ynolates are converied into reactive species after the first reaction. Using this property, novel successive reactions as well as new synthetic method of ynolates have been developed1. Practical synthetic method of ynolates: Naphithalene catalyzed reductive lithation of dibromo esters leading ynolates was developed.2. Highly Z-selective synthesis of alkenes via tandem [2+2] cycloaddition - ring-opening reaction: Ynolates reacted with acylsilanes to afford polysubstituted vinyl silanes with perfect Z-selectivity. These vinyl silanes produced can be converted into tetrasubstituted alkenes. Ynolates reacted with α-oxyketones to give tetrasubsituted alkenes with high Z-selectivity. These prodeucts were easily converted into butenolides by treatment of acids. This 2-step conversion prosess can be carried out in one-pot.3. Efficient syntheses of carbocycles via tandem [2+2] cycloaddition - Michael reaction: β-Lactone enolates prepared by reaction of ynolates with ketones have high nucleophiliciy. The reaction of ynolates with ketones having an unsaturated eater unit in a proper positionprovided bicyclic β-lactones via tandem [2+2] cycloaddition - Michael addition. The products were easily converted to polysubstituted cycloalkenes in good yield. By this tandem reaction, five-, six- and seven-membered carbocycles can be constructed. Since the products of the tandem reaction are ester enolates, they have uncleophilicity. Taking advantage of this properties, cascade reactions can be carried out to give complex molecules.4. Total synthesis of cucumin E, novel type of triquinane sesquiterpenoid, was achieved using the tandem reaction.