Efficient Enantioselective Synthesis of Dihydropyrans Using a Chiral N,N′-Dioxide as Organocatalyst
摘要:
The bifunctional organocatalyst C3 N,N'-dioxide has been successfully applied to the asymmetric cascade Michael/hemiacetalization reaction of alpha-substituted cyano ketones and beta,gamma-unsaturated alpha-ketoesters for the synthesis of multifunctionalized chiral dihydropyrans. The corresponding products were obtained in excellent yields (up to 99%) with high to excellent enantioselectivities (up to 99% ee).
A new method for the generation of benzyl radicalsfrom acetals via low-valent titanium-mediated homolytic C–O bond cleavage is presented. The low cost and availability of the developed titanium reagent enable efficient access to α-alkoxy carbon radicalspecies via the developed reaction.
A Novel Approach to the Practical Synthesis of Sulfides: An InBr<sub>3</sub>-Et<sub>3</sub>SiH Catalytic System Promoted the Direct Reductive Sulfidation of Acetals with Disulfides
Rearrangement of Hydroxylated Pinene Derivatives to Fenchone-Type Frameworks: Computational Evidence for Dynamically-Controlled Selectivity
作者:Marcus Blümel、Shota Nagasawa、Katherine Blackford、Stephanie R. Hare、Dean J. Tantillo、Richmond Sarpong
DOI:10.1021/jacs.8b05804
日期:2018.7.25
An acid-catalyzed Prins/semipinacolrearrangementcascade reaction of hydroxylated pinene derivatives that leads to tricyclic fenchone-type scaffolds in very high yields and diastereoselectivity has been developed. Quantum chemical analysis of the selectivity-determining step provides support for the existence of an extremely flat potential energy surface around the transition state structure. This
Multicomponent Aromatic and Benzylic Mannich Reactions through C−H Bond Activation
作者:Tania Xavier、Corinne Rayapin、Erwan Le Gall、Marc Presset
DOI:10.1002/chem.201903414
日期:2019.10.28
Multicomponent Mannich reactions through C-H bond activation are described. These transformations allowed for the straightforward generation of densely substituted benzylic and homo-benzylic amines in good yields. The reaction involves a reaction between two transient species: an organometallic species, generated by transition-metal-catalyzed sp2 or sp3 C-H bond activation and an in situ generated
A new generation of aprotic yet Brønsted acidic imidazolium salts: low toxicity, high recyclability and greatly improved activity
作者:Lauren Myles、Rohitkumar G. Gore、Nicholas Gathergood、Stephen J. Connon
DOI:10.1039/c3gc40975a
日期:——
Catalysts which have low antimicrobial toxicity and are aprotic, yet which can act as Brønsted acidic catalysts in the presence of protic additives have been developed. The catalysts are recyclable, considerably more active (i.e. can be used at 10–50 times lower loadings) and of broader scope than their antecedent generation.