Synthesis of 2‘,3‘-Dideoxy-2‘-trifluoromethylnucleosides from α-Trifluoromethyl-α,β-unsaturated Ester
作者:Xingang Zhang、Feng-Ling Qing、Yihua Yu
DOI:10.1021/jo005520r
日期:2000.10.1
beta-unsaturated esters 3. The trifluoromethylation of (Z)/(E)-ethyl 3-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-bromo-2-propenoate (2e), which is derived from 1-(R)-glyceraldehydeacetonide, yields the key intermediate alpha-trifluoromethyl-alpha,beta-unsaturated esters 3e. This is transformed into anomeric acetates 8a and 8b and is used for the synthesis of a number of 2', 3'-dideoxy-2'-trifluoromethylnucleosides
A convenient synthetic method was reported for the preparation of N-phthaloyl dehydroamino acid esters from easily accessible vinylbromides (or vinyl tosylate) and potassium phthalimide. Rh-catalyzed asymmetric hydrogenation of these substrates with TangPhos gave the products with good to excellent enantioselectivities (up to 99% ee).
A new protocol for the alkenylation of carbonyl compounds with phosphonates (Horner-Wadsworth-Emmons reaction) is described. Aldehydes react with phosphonates already at room temperature in the presence of triethylamine without further activation by Lewis-acids if high-pressure (8 kbar) is applied to the system. Based on this protocol a domino process was developed combining the HWE reaction with a Michael reaction, thus allowing the one-pot synthesis of β-amino esters, β-thio esters or β-thio nitriles.
Abstract (2Z)-α-Bromo-α,β-unsaturated esters 6 can be synthesized stereoselectiveviaarsoniumylides in good yields.
摘要 (2Z)-α-溴-α,β-不饱和酯 6 可以立体选择性地通过砷叶立德合成,收率良好。
Microwave-Assisted Tandem Nucleophilic Substitution-Wittig Reaction of α<i>-</i>Hypervalent Iodine Functionalized Phosphonium Ylide
作者:Xian Huang、Xiaochun Yu
DOI:10.1055/s-2002-34893
日期:——
Under microwave irradiation conditions the tandem nucleophilic substitution-Wittig reaction of α-hypervalent iodine functionalized phosphonium ylide can occur readily to afford α-heteroatom substituted-α,β-unsaturated enoates in good yields stereoselectively.