6‐bis(oxazoline) (pybox) ligands for asymmetric transition metal catalysis is introduced by adding a bidentate ligand to modulate the electronic properties and asymmetric induction. Specifically, a ruthenium(II) pybox fragment is combined with a cyclometalated N‐heterocyclic carbene (NHC) ligand to generate catalysts for enantioselective transition metal nitrenoid chemistry, including ring contraction
通过添加双齿配体来调节电子性质和不对称诱导,提出了扩大手性吡啶-2,6-双(恶唑啉)(pybox)配体在不对称过渡金属催化中的应用的策略。具体来说,钌 (II) pybox 片段与环金属化 N-杂环卡宾 (NHC) 配体结合,生成用于对映选择性过渡金属氮烯化学的催化剂,包括环收缩为手性 2H-氮丙啶(2000 TON 时高达 97% ee)和对映选择性 C(sp 3 )−H 胺化(50 TON 时高达 97 % ee)。
Asymmetric Synthesis of 2<i>H</i>
-Azirines with a Tetrasubstituted Stereocenter by Enantioselective Ring Contraction of Isoxazoles
Highly strained 2H‐azirines with a tetrasubstituted stereocenter were synthesized by the enantioselective isomerization of isoxazoles with a chiral diene–rhodium catalyst system. The effect of ligands and the coordination behavior support the proposed catalytic cycle in which the coordination site is fixed in favor of efficient enantiodiscrimination by a bulky substituent of the ligand. In silico studies
the synthesis of azirine-2-carboxylates from non-halogenated 5-alkoxyisoxazoles. A convenient gram-scale method for the preparation of 2-halo-2H-azirine-2-carboxylic acidesters, thioesters and amides via metal-catalyzed isomerization of 5-heteroatom-substituted 4-haloisoxazoles is developed. The formation of the esters and amides is efficiently catalyzed by Rh2(Piv)4, while FeCl2·4H2O is the catalyst
Gold vs Light: Chemodivergent Reactivity of Diazoesters toward 2<i>H</i>-Azirine-2-carboxylic Acids
作者:Gleb D. Titov、Grigory I. Antonychev、Mikhail S. Novikov、Alexander F. Khlebnikov、Elizaveta V. Rogacheva、Liudmila A. Kraeva、Nikolai V. Rostovskii
DOI:10.1021/acs.orglett.3c00823
日期:2023.4.21
reaction is N-selective and produces 1,3-oxazin-6-ones, whereas a blue light activation leads to O–H insertion products, azirine-2-carboxylic esters. The observed chemodivergence is explained by the metal-bound and metal-free carbenes exhibiting different electronic properties in these reactions. In addition, a high antibacterial potential of the 1,3-oxazin-6-ones synthesized is shown.