- Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides
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New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines.
- Ong, Derek Yiren,Yen, Zhihao,Yoshii, Asami,Revillo Imbernon, Julia,Takita, Ryo,Chiba, Shunsuke
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supporting information
p. 4992 - 4997
(2019/03/13)
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- Application of 13C NMR Spectroscopy and 13C-Labeled Benzylammonium Salts to the Study of Rearrangements of Ammonium Benzylides
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Ylides generated from N-(cyanomethyl)-N,N-dimethyl-N-[α-(trimethylsilyl)benzyl]ammonium chloride (4) and fluoride anion afford the products of [1,2] shift 11 and [2,3] shift 13. Formation of product 13 shows that, in the presence of water from TBAF, rearrangements and [1,3]H shift in ylide intermediates become competitive processes. The reaction of N-benzyl-N,N-dimethyl-N-[α-(trimethylsilyl)benzyl]ammonium bromide (5) and 13C labeled (at the benzyl carbon) salt 5* gave a mixture of 10, 14, and 15 as products of [1,4], [1,2], and [2,3] rearrangement, respectively. 13C NMR spectra of products derived from salt 5* exclude [1,3]H shift in ylide 9a+-. Rearrangement of ylides generated from N-benzyl-N,N-dimethyl-N-[(dimethylphenylsilyl)methyl]ammonium bromide (6*) (enriched in 13C at benzyl carbon) and n-BuLi reveals that N,N-dimethyl-2-[(dimeth-ylphenylsilyl)methyl]benzylamine (20*) is not formed by a [1,4] shift but instead, via a [2,3] shift in silylmethylide followed by subsequent [1,4]Si and [1,2]H shift, as previously suggested in the literature. This mechanism is unique to some silyl-substituted ylides.
- Zdrojewski, Tadeusz,Jończyk, Andrzej
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p. 452 - 457
(2007/10/03)
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- Synthesis of 5-alkylidene-6-(dimethylamino)methyl-1,3-cyclohexadienes from α-substituted benzyldimethylammoniomethylides
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2-Substituted 5-alkylidene-6-(dimethylamino)methyl-1,3-cyclohexadienes (E)-4 and (Z)-4 were prepared by the reaction of α,4-disubstituted dimethyl[(trimethylsilyl)methyl]benzylammonium iodides 2 with cesium fluoride. Their E-isomers were stable at room temperature and could be used in the Diels-Alder reaction. Some related reactions are also described.
- Machida,Shirai,Sato
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p. 117 - 122
(2007/10/02)
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