METAL-ION EFFECTS IN WITTIG REACTIONS - A GENERAL HYPOTHESIS FOR THE MECHANISM OF THE WITTIG REACTION

被引:59
作者
WARD, WJ [1 ]
MCEWEN, WE [1 ]
机构
[1] UNIV MASSACHUSETTS, DEPT CHEM, AMHERST, MA 01003 USA
关键词
D O I
10.1021/jo00289a021
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
To evaluate better the effects of N2p-P(IV) through-space interactions in Wittig reactions, a thorough study of metal ion effects in Wittig reactions lacking such interactions has been completed. As in the case of Wittig reactions with stabilized ylides, it has been determined that, with a moderated ylide, the stereochemistry (E:Z ratio) of alkene formation with an aldehyde is determined at the point that a new carbon—carbon bond has been formed to give a betaine or an oxaphosphetane intermediate. The observations that in most cases where lithium ion is present, the product mixture is enriched with the Z alkene, while when sodium or potassium ions are present, the E isomer predominates, are deemed to support the concept that a spin-paired diradical is formed as an unstable intermediate when sodium or potassium ions are present but that an ionic reaction occurs when lithium ions are present. The evidence that has been accumulated suggests that the reactions studied here (involving aromatic, heterocyclic, and aliphatic aldehydes and benzylidenediphenylmethylphosphorane or the preformed betaines, in THF at -78 °C) occur under kinetic control and without any significant degree of equilibration or Wittig reversal. © 1990, American Chemical Society. All rights reserved.
引用
收藏
页码:493 / 500
页数:8
相关论文
共 49 条
[1]   ALKALINE HYDROLYSIS OF SOME TRI-(2-THIENYL)PHOSPHONIUM SALTS - INDUCTIVE EFFECTS ON RATE OF NUCLEOPHILIC ATTACK AT PHOSPHORUS [J].
ALLEN, DW .
JOURNAL OF THE CHEMICAL SOCIETY B-PHYSICAL ORGANIC, 1970, (08) :1490-&
[2]  
BAGAVANT C, 1973, P INDIAN ACAD SCI A, V77, P6
[3]   PHENYLCINNAMALONES .2. SOME DATA CONCERNING PREPARATIVE REACTION [J].
BEDNOWITZ, AL ;
BROWN, RG ;
DONARUMA, LG ;
HAMILTON, WC ;
KROPF, RA ;
SOUTHWICK, PL ;
STANSFIELD, RE .
JOURNAL OF ORGANIC CHEMISTRY, 1974, 39 (24) :3537-3543
[4]   STEREOCHEMISTRY OF WITTIG REACTION WITH NON-STABILIZED AND SEMISTABILIZED YLIDS [J].
BERGELSON, LD ;
BARSUKOV, LI ;
SHEMYAKIN, MM .
TETRAHEDRON, 1967, 23 (06) :2709-+
[5]  
BUCKOWSKI Z, 1970, B ACAD POL SCI SC, V18, P577
[6]   APPARENT ABSENCE OF REVERSAL OF OXAPHOSPHETANE FORMATION IN SOME WITTIG REACTIONS [J].
CAIRNS, SM ;
MCEWEN, WE .
TETRAHEDRON LETTERS, 1986, 27 (14) :1541-1544
[7]   METHYLSULFINYL CARBANION (CH3-SO-CH2-) . FORMATION AND APPLICATIONS TO ORGANIC SYNTHESIS [J].
COREY, EJ ;
CHAYKOVSKY, M .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1965, 87 (06) :1345-+
[8]   CAPTO-DATIVE SUBSTITUENT EFFECT ON THE CIS-TRANS ISOMERIZATION OF CYCLOPROPANES .11. [J].
DEMESMAEKER, A ;
VERTOMMEN, L ;
MERENYI, R ;
VIEHE, HG .
TETRAHEDRON LETTERS, 1982, 23 (01) :69-72
[9]   MECHANISM OF THE DIELS-ALDER REACTION - STUDIES OF THE ADDITION OF MALEIC-ANHYDRIDE TO FURAN AND METHYLFURANS [J].
DEWAR, MJS ;
PIERINI, AB .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1984, 106 (01) :203-208
[10]   MULTIBOND REACTIONS CANNOT NORMALLY BE SYNCHRONOUS [J].
DEWAR, MJS .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1984, 106 (01) :209-219