The oxadi-π-methane rearrangement of 2,4-cyclohexadienones to bicyclic ketones was found to proceed with high enantioselectivity (92–97% ee) in the presence of catalytic amounts of a chiral Lewisacid (15 examples, 52–80% yield). A notable feature of the transformation is the fact that it proceeds on the singlet hypersurface and that no triplet intermediates are involved. Rapid racemic background reactions
reaction of aromaticaldehydes and arylketones with a silylboronate in the presence of a catalytic amount of a CuCl-N-heterocyclic carbene (NHC) complex and a stoichiometric amount of alkoxide base yielded cross-coupled 1,2-diol derivatives. A reaction pathway is proposed that involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species from the aromaticaldehyde and its subsequent
A Cooperative N-Heterocyclic Carbene/Chiral Phosphate Catalysis System for Allenolate Annulations
作者:Anna Lee、Karl A. Scheidt
DOI:10.1002/anie.201403446
日期:2014.7.14
The highly enantioselective NHC‐catalyzed [3+2] annulation reaction with α,β‐alkynals and α‐ketoesters has been developed. A new mode of cooperativecatalysis involving the combination of a chiral Brønsted acid and a C1‐symmetric biaryl saturated‐imidazolium precatalyst was required to generate the desired γ‐crotonolactones in high yields and levels of enantioselectivity.
已开发出高对映选择性 NHC 催化的 [3+2] 与 α,β-炔醛和 α-酮酯的环化反应。需要一种新的协同催化模式,包括手性布朗斯台德酸和 C 1对称联芳基饱和咪唑鎓预催化剂的组合,以高产率和对映选择性水平生成所需的 γ-巴豆内酯。
Electrochemical Synthesis of Sultone Derivatives via Dehydrogenative C–O Bond Formation
作者:Koichi Mitsudo、Yasuyuki Okumura、Kotaro Yohena、Yuji Kurimoto、Eisuke Sato、Seiji Suga
DOI:10.1021/acs.orglett.3c01062
日期:2023.5.19
Electrochemical dehydrogenative C–O bond formation for the synthesis of sultones was achieved. In the presence of K2CO3 and H2O, constant current electrolysis of [1,1′-biphenyl]-2-sulfonyl chloride afforded an aryl-fused sultone quantitatively. Under the optimized conditions, a variety of sultone derivatives were obtained. Control experiments suggest that the electrochemical oxidation of the sulfonates
实现了用于合成磺内酯的电化学脱氢 C-O 键形成。在K 2 CO 3和H 2 O存在下,恒流电解[1,1'-联苯]-2-磺酰氯定量得到芳基稠合磺内酯。在优化条件下,得到了多种磺内酯衍生物。对照实验表明,原位产生的磺酸盐的电化学氧化会提供磺基中间体。
Asymmetric Homoenolate Additions to Acyl Phosphonates through Rational Design of a Tailored <i>N</i>-Heterocyclic Carbene Catalyst
作者:Ki Po Jang、Gerri E. Hutson、Ryne C. Johnston、Elizabeth O. McCusker、Paul H.-Y. Cheong、Karl A. Scheidt
DOI:10.1021/ja410932t
日期:2014.1.8
A highly selective NHC-catalyzed synthesis of gamma-butyrolactones from the fusion of enals and alpha-ketophosphonates has been developed. Computational modeling of competing transition states guided a rational design strategy to achieve enhanced levels of enantioselectivity with a new tailored C-1-symmetric biaryl-saturated imidazolium-derived NHC catalyst.