Direct synthesis of 4,4-disubstituted N-silyl-1,4-dihydropyridines
作者:Jan Bräckow、Klaus T. Wanner
DOI:10.1016/j.tet.2005.11.069
日期:2006.3
based on the trapping reaction of 4-substitued N-silylpyridinium ions. When performed with dialkylmagnesiumreagents, such as iPr2Mg, silyl protected 4,4-disubstituted 1,4-dihydropyridines were obtained in up to quantitative yields. High 1,4-selectivity was found for sterically demanding nucleophiles, whereas small nucleophiles (Me2Mg) tend to yield 1,2-addition-products. Grignard, dialkylzinc and organocopper
Infrared and nuclear magnetic resonance spectroscopic studies of the structure and dynamics of allylic magnesium compounds
作者:E Alexander Hill、Winston A Boyd、Hemnalini Desai、Amir Darki、Lymel Bivens
DOI:10.1016/0022-328x(95)06014-n
日期:1996.5
streching bONds, corresponding to C  CH2 and C  CD2 groups in equilibrating allylic isomers. The methylene resonances in the 13C NMR spectra of allylmagnesium bromide and chloride and methallylmagnesium bromide are broadened at low temperatures by an exchange process which appears to be the interconversion between the classical unsymmetrical allytic structures. Analogous changes are seen in the spectrum
烯丙基-和甲基烯丙基-d 2-溴化镁的红外光谱具有两个双键拉伸键,对应于平衡烯丙基异构体中的CCH 2和C 2 CD 2基团。13中的亚甲基共振烯丙基溴化镁和氯化物以及甲基烯丙基溴化镁的13 C NMR光谱在低温下通过交换过程扩大,这似乎是经典不对称解析结构之间的相互转化。在1,3-二甲基烯丙基氯化镁的光谱和烯丙基溴化镁的质子NMR光谱中可以看到类似的变化。交换的速率常数和激活参数已从线宽确定。与格利雅试剂不同,二甲基镁在四氢呋喃中的亚甲基共振在降低的温度下不会显着加宽,并且氘代试剂在红外光谱中没有两个明显的双键拉伸带。
Determination of the absolute stereochemistry of the antifungal antibiotic YM-47522 by the total synthesis of its enantiomer
作者:Mikhail S. Ermolenko
DOI:10.1016/s0040-4039(96)01466-9
日期:1996.9
The enantiomer 1 of the new antifungal antibiotic YM-47522 has been synthesized and found to be the antipode of the natural product. Thus, the absolutestereochemistry of the naturally occurring antibiotic YM-47522 was determined to be (7S, 8S, 9R, 10S).
Additions of Organomagnesium Halides to α-Alkoxy Ketones: Revision of the Chelation-Control Model
作者:Jacquelyne A. Read、Yingying Yang、K. A. Woerpel
DOI:10.1021/acs.orglett.7b01161
日期:2017.7.7
obtained in additions of organometallic nucleophiles to α-alkoxy ketones but fails for reactions of allylmagnesium halides. Low diastereoselectivity in ethereal solvents results from no chelation-induced rate acceleration. Additions of allylmagnesium bromide to carbonyl compounds are diastereoselective using CH2Cl2 as the solvent even though rate acceleration is still absent. Stereoselectivity likely arises
Synthesis of the originally proposed structures of elatenyne and an enyne from Laurencia majuscula
作者:Helen M. Sheldrake、Craig Jamieson、Sofia I. Pascu、Jonathan W. Burton
DOI:10.1039/b814953d
日期:——
A bidirectional synthesis of the originally proposed structures for the natural products elatenyne and a chloroenyne from Laurencia majuscula is described along with a reassessment of the structures of the halogenated enynes based upon a 13C NMR chemical shift/structure correlation.