Preference for eclipsed conformations in acyclic neopentyldialkylamines and the stereodynamical consequences: An NMR and molecular mechanics investigation

被引:14
作者
Anderson, JE [1 ]
Casarini, D [1 ]
Ijeh, AI [1 ]
Lunazzi, L [1 ]
机构
[1] UNIV BOLOGNA,DEPT ORGAN CHEM A MANGINI,I-40136 BOLOGNA,ITALY
关键词
D O I
10.1021/ja9710363
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A dynamic NMR study of a number of acyclic N,N-dialkylneopentylamines, supported by molecular mechanics calculations, is reported. With simple alkyl groups, eclipsed conformations are encountered for the NCH2But bond, which has a high I-fold rotational barrier. The N-inversion/rotation process for Me2NCH2But was rendered detectable by desymmetrizing the molecule as Me2NCHDBut. Here the decoalescence of separate C-13 signals for the diastereotopic NMe groups allowed the measurement of the corresponding free energy of activation (Delta G(double dagger) = 9.4 kcal mol(-1)). With significantly more branched alkyl groups, the N-CH2But bond adopts a conformation intermediate between staggered and eclipsed. Trineopentylamine and an analogue undergo a novel concerted back and forward 60 degrees rotation through eclipsed conformations about the N-CH2But bonds, with a barrier which dynamic NMR indicates must be at least 8.3 kcal mol(-1).
引用
收藏
页码:8050 / 8057
页数:8
相关论文
共 36 条
[31]   AN APPLICATION OF STATISTICAL DESIGN TO ORGANIC SYNTHESIS - THE REDUCTIVE ALKYLATION OF TERT-BUTYLAMINE (LEUCKART REACTION) [J].
MEINERS, AF ;
BOLZE, C ;
SCHERER, AL ;
MORRISS, FV .
JOURNAL OF ORGANIC CHEMISTRY, 1958, 23 (08) :1122-1125
[32]  
MOORE ML, 1949, ORG REACTIONS, V5, P307
[33]   LONG-LIVED TRIALKYLAMINE RADICAL CATIONS CONTAINING C-ALPHA-H BONDS IN ACYCLIC ALKYL-GROUPS [J].
NELSEN, SF ;
CUNKLE, GT .
JOURNAL OF ORGANIC CHEMISTRY, 1985, 50 (20) :3701-3705
[34]   STRUCTURE AND CONFORMATION OF DIHYDRO AROMATIC-COMPOUNDS .3. CIS-DISUBSTITUTED AND TRANS-DISUBSTITUTED 1,4-DIHYDROBENZENES, 1,4-DIHYDRONAPHTHALENES, AND 9,10-DIHYDROANTHRACENES [J].
RABIDEAU, PW ;
LIPKOWITZ, KB ;
NACHBAR, RB .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1984, 106 (11) :3119-3123
[35]  
Sandstrom J., 1982, Dynamic NMR Spectroscopy
[36]   TRICYCLIC ORTHOAMIDES - EFFECTS OF LONE-PAIR ORIENTATION UPON NMR-SPECTRA [J].
WEISMAN, GR ;
JOHNSON, V ;
FIALA, RE .
TETRAHEDRON LETTERS, 1980, 21 (38) :3635-3638