Diastereoselectivity in the McLafferty rearrangement of photoionized 3-methyl valeramide

被引：17

作者：

Loos, J ^{[1
]}

Schröder, D ^{[1
]}

Schwarz, H ^{[1
]}

机构：

[1] Tech Univ Berlin, Inst Chem, D-10623 Berlin, Germany

来源：

JOURNAL OF ORGANIC CHEMISTRY | 2005年 / 70卷 / 03期

关键词：

D O I：

10.1021/jo0482458

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

The McLafferty rearrangement of photoionized 3-methyl valeramide proceeds quasi-barrierless and with high regio-selectivity. The mass spectra of the stereospecifically labeled syn- and anti-[4-D-1]-diastereomers reveal a strong preference for activation of the gamma-hydrogen/deuterium in anti-position relative to the methyl group at C(3), which serves as a steric marker. Quantitative analysis of the fragmentation patterns of other photoionized isotopomers permits the determination of primary and secondary kinetic isotope effects (KIEs), the branching ratios of competing McLafferty reactions, and the steric effect (SE) associated with transfer of the diastereotopic H(D) atoms at C(4). While the associated KIEs of the title reaction are negligible, the steric effect (SE = 2.9) is remarkably large for the otherwise flexible, monofunctional compound. The findings can be explained by a preferentially chairlike transition structure for the initial gamma-H atom transfer.

引用

页码：1073 / 1076

页数：4

共 25 条

[1]

AUDIER HE, 1965, B SOC CHIM FR, P3236

[2] A state-selected study of Ar+(P-2(3/2,1/2))+O-2 charge transfer at collision energies below 4 eV using synchrotron radiation and guided beam techniques [J].