Copper-Catalyzed 1,6-Hydrodifluoroacetylation of<i>para</i>-Quinone Methides at Ambient Temperature with Bis(pinacolato)diboron as Reductant
作者:Miaolin Ke、Qiuling Song
DOI:10.1002/adsc.201600991
日期:2017.2.2
6‐hydrodifluoroacetylation of para‐quinone methides with difluoroalkyl bromides has been described with bis(pinacolato)diboron (B2pin2) as reductant. In this reaction, a new C(sp3)–CF2 bond is constructed under smart conditions. A broad substrate scope of para‐quinone methides (p‐QMs) make this protocol very practical and attractive. Preliminary mechanisticstudies manifested that a difluoroalkyl radical
Isothiourea-Catalyzed Enantioselective α-Alkylation of Esters via 1,6-Conjugate Addition to para-Quinone Methides
作者:Jude N. Arokianathar、Will C. Hartley、Calum McLaughlin、Mark D. Greenhalgh、Darren Stead、Sean Ng、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.3390/molecules26216333
日期:——
initial N-acylation of the isothiourea by the para-nitrophenyl ester, is proposed to facilitate catalyst turnover in this transformation. A range of para-nitrophenyl ester products can be isolated, or derivatized in situ by addition of benzylamine to give amides at up to 99% yield. Although low diastereocontrol is observed, the diastereoisomeric ester products are separable and formed with high enantiocontrol
Basicities and Nucleophilicities of Pyrrolidines and Imidazolidinones Used as Organocatalysts
作者:Feng An、Biplab Maji、Elizabeth Min、Armin R. Ofial、Herbert Mayr
DOI:10.1021/jacs.9b11877
日期:2020.1.22
the attack of the amines at the electrophiles to be determined. The resulting second-order rate constants k2 followed the correlation log k2(20 °C) = sN(N + E), where electrophiles are characterized by one parameter (E) and nucleophiles are characterized by the two solvent-dependent parameters N and sN. In this way, the organocatalysts A1-A32 were integrated in our comprehensive nucleophilicity scale
Presented is the first enantioselective copper‐catalyzed 1,6‐conjugateaddition of bis(pinacolato)diboron to para‐quinonemethides. The reaction proceeds with excellent yields and good to excellent enantioselectivities, and provides an attractive approach to the construction of optically active gem‐diarylmehtine boronic esters. Additionally, the subsequent conversion of the derived potassium trifluoroborates
An asymmetric 1,6‐conjugate addition of thioacetic acid with para‐quinone methides has been developed by using chiral phosphoric acid catalysis in the presence of water. A series of sulfur‐containing compounds were thus obtained in high yields with good to excellent enantioselectivities. Theoretical studies indicated that the water‐bridged proton transfer is a potentially favorable reaction pathway