Aza-[1,2]-Wittig rearrangements of N-benzyl glycine methyl esters. A new approach to the synthesis of N-aryl phenylalanine derivatives

Tetrahedron Letters

Volumn 56, Issue 23, 2015, Pages 3393-3395

  Everett, Renata K ^a   Wolfe, John P ^a  

^a UNIVERSITY OF MICHIGAN   (United States)

Author keywords

Boron; Enolate; Heterocycle; Wittig rearrangement

Indexed keywords

1,4,2 OXAZABOROLE DERIVATIVE; ANILINE DERIVATIVE; BENZALDEHYDE DERIVATIVE; CARBONYL DERIVATIVE; ESTER DERIVATIVE; GLYCINE METHYL ESTER; HYDROGEN PEROXIDE; N ARYL PHENYLALANINE DERIVATIVE; N BENZYL GLYCINE METHYL ESTER; PHENYLALANINE DERIVATIVE; PHENYLALANINE METHYL ESTER; UNCLASSIFIED DRUG;

ALDOL REACTION; ARTICLE; DECOMPOSITION; DIASTEREOISOMER; HYPOTHESIS; REACTION TIME; SYNTHESIS; TEMPERATURE; WITTIG REARRANGEMENT; X RAY CRYSTALLOGRAPHY;

EID: 84929645785     PISSN: 00404039     EISSN: 18733581     Source Type: Journal    
DOI: 10.1016/j.tetlet.2015.01.037     Document Type: Article

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18. When a single equivalent of dibutylboron triflate was used the rearrangement reaction proceeded to 74% conversion (26% unreacted starting material) as judged by 1H NMR analysis. This experiment suggests that the reaction proceeds through a boron enolate that contains a single equivalent of an organoboron species, rather than an intermediate that bears two dialkylboron units (one bound to oxygen and one bound to nitrogen). We have elected to classify this as a Wittig-type rearrangement as it does not appear that an ammonium ion resulting from protonation of the amino group (as in a Stevens-type rearrangement) is required. However, there likely is a Lewis acid/base chelate interaction between the O-BR2 group and the amino group, so in this case there may not be a clean division between classification as a Wittig rearrangement versus a Stevens rearrangement.
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