Enantioselective Diarylcarbene Insertion into Si–H Bonds Induced by Electronic Properties of the Carbenes
作者:Liang-Liang Yang、Declan Evans、Bin Xu、Wen-Tao Li、Mao-Lin Li、Shou-Fei Zhu、K. N. Houk、Qi-Lin Zhou
DOI:10.1021/jacs.0c04725
日期:2020.7.15
enantioselection usually depends on differences in steric interactions between prochiral substrates and a chiral catalyst. We have discovered a carbene Si-H insertion in which the enantioselectivity depends primarily on the electronic characteristics of the carbene substrate, and the log(er) values are linearly related to Hammett parameters. A new class of chiral tetraphosphate dirhodium catalysts was developed
Intermediates in the decomposition of aliphatic diazo-compounds. Part XII. Chemically induced dynamic polarisation of fluorine-19 and proton nuclei in the insertion of diarylmethylenes into benzyl fluoride
作者:Donald Bethell、Max R. Brinkman、John Hayes、Kenneth McDonald
DOI:10.1039/p29760000966
日期:——
of phenyl t-butyl nitrone which traps intermediate free radicals it is shown that polarised insertionproducts arise from both recombination of geminate radical pairs and from diffusive encounter of diarylmethyl and fluorobenzyl radicals. The results, particularly the differential effect of substituent on the polarisation of 19F and 1Hnuclei, are interpretable in terms of the radical-pair theory of
描述了在溶剂苄基氟中二芳基重氮甲烷热分解过程中形成的2,2-二芳基-1-苯基乙基氟化物的19 F和1 H nmr信号的极化模式。使用二苯基重氮甲烷时,19 F四重峰显示净(A)+多重峰(A / E)极化,并且随着g的变化变为E + A / E。使用取代的二苯基重氮甲烷,中间体二芳基甲基自由基的α-因子增加到超过2.003 0。用单取代的二苯基重氮甲烷,可以等量形成两个非对映异构产物,并且它们显示出相同的极化。在几乎取代基的整个范围内,小净极化是在对尽管Δ大范围变化的氟质子孪位和邻位的NMR信号检测克; 两者1H四重奏显示出强大的多重极化,H-1的A / E和H-2的E / A。通过使用捕获中间自由基的苯基叔丁基硝酮,表明极化的插入产物既来自双键自由基对的重组,也来自二芳基甲基和氟苄基的扩散相遇。结果,特别是取代基对19 F和1 H原子极化的微分作用,可以用CIDNP的自由基对理论来解释,但
Synthesis of 4-nitroisoxazoline N-oxides
作者:F. A. Gabitov、O. B. Kremleva、A. L. Fridman
DOI:10.1007/bf00470554
日期:1978.3
New metallocene complexes of Nb and Ta with functionalized diazoalkanes
The reaction of Cp2MH3, where M = Nb or Ta, with N2CPh2, N2CPh(o-C6H4Br) and N2CHCOOEt was thoroughly studied. It was shown that the primary products of the reaction are the complexes Cp2M(H)(eta1-N2CRR') (2). The complexes 2 are readily oxidized by air to give polymeric (Cp2MO)n, N2CRR' and RR'CN2CRR'.Interaction of an excess of N2CPh(o-C6H4Br) with Cp2NbH3 leads to a 17-electron complex Cp2Nb(-N-N=CPh-o-C6H4)2 (6) with two sigma-N pyrazole ligands. Finally the reaction of Cp2NbH3 with N2CHCOOEt gives an unusual dimeric complex Cp2Nb2(eta5-C5H4C(COOEt)=N-mu-N)2. The complexes 2 were found to undergo easily substitution of a hydride ligand for a halogen atom.The results of X-ray analysis of the complexes 6 and Cp2Nb(Cl)-eta1-N2CPh(o-C6H4Br) are provided.
GABITOV F. A.; KREMLEVA O. B.; FRIDMAN A. L., XIMIYA GETEROTSIKL. SOEDIN., 1978, HO