A transition-metal free synthesis of highly functionalized 2-hydroxy-2′-amino-1,1′-biaryls from N-arylhydroxylamines has been developed. This operationally simple and readily scalable approach relies on a cascade of reactions that initially generates transient N,O-diarylhydroxylamines, via direct O-arylation, which then undergo rapid [3,3]-sigmatropic rearrangement and subsequent rearomatization to
From β-Nitrothiophenes to Ring-Fused Nitrobenzenes: An Overall Ring-Enlargement Process via a Facile, Aromatization-Driven, Thermal 6π Electrocyclization<sup>1</sup>
the 3-unsubstitutedderivatives 8, deriving from the initial ringopening of 3-nitrothiophene (2), have been likewise found herein to undergo cyclization, followed by aromatization, in analogous mild experimental conditions, leading to the ring-fused homo- or heteroaromatic nitro derivatives 10. The concerted electrocyclic nature of the process is strongly supported by the outcome of tests based on
synthesis of functionalized biaryls through nucleophilic aromatic substitution (SNAr) of arylhydroxylamines to arylsulfoniumsalts. With this protocol, structurally diverse functionalized biaryls were obtained smoothly in moderate to good yields. Merits of this transformation include mild reaction conditions, broad substrate scope, great functional group tolerance, feasibility of a one-pot procedure, and
我们报告了一种无过渡金属方案,用于通过芳基羟胺到芳基锍盐的亲核芳族取代 (S N Ar) 合成功能化联芳基化合物。使用该协议,结构多样的功能化联芳基以中等至良好的产量顺利获得。这种转化的优点包括反应条件温和、底物范围广、官能团耐受性好、一锅法的可行性以及易于处理和放大。
Escherichia coli strains which over-produce L-thereonine and processes for the production of L-threonine by fermentation
申请人:——
公开号:US20020106800A1
公开(公告)日:2002-08-08
The present invention relates to the fields of microbiology and microbial genetics. More specifically, the invention relates to novel bacterial strains and processes employing these strains for the fermentative production of amino acids such as threonine.