Enantioselective Addition of Thiazolyllithiumto Aldimines with the Aid of Chiral Ligand. Asymmetric Synthesis of (S)-Doe, a Component of Marine Natural Product, Dolastatin 10
摘要:
The external chiral ligand mediated asymmetric reaction of thiazolyllithium with aldimines was examined. The amino ether (5) gave rise to relatively high selectivity in the reaction of phenylimine, and sparteine (6) provided high selectivity in the reaction of imines bearing an alpha-methylene group. The reaction was applied to the synthesis of (S)-Doe, a component of antileukemic marine natural product, dolastatin 10.
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.
addition of PhSeCl to α- and β-substituted styrenes in methanol is regio- and stereospecific and affords the products of methoxyselenenylation. These compounds further react with PhSeCl to give the deselenenylation products. In the case of α-substituted styrenes, 1-methoxy, 2-chloroalkanes are produced, whereas with β-substituted styrenes the major reaction products are the 1,2-dimethoxyalkanes and
Photolysis of α-Azidoacetophenones: Direct Detection of Triplet Alkyl Nitrenes in Solution
作者:Pradeep N. D. Singh、Sarah M. Mandel、Rachel M. Robinson、Zhendong Zhu、Roberto Franz、Bruce S. Ault、Anna D. Gudmundsdóttir
DOI:10.1021/jo034674e
日期:2003.10.1
of triplet alkyl nitrenes in fluid solution by laser flash photolysis of alpha-azido acetophenone derivatives, 1. Alphazides 1 contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1 cleave to form benzoyl and methylazide radicals in competition with triplet energy transfer to form
Hypoiodous acid-catalyzed regioselective geminal addition of methanol to vinylarenes: synthesis of anti-Markovnikov methyl acetals
作者:Swamy Peraka、Naresh Mameda、Mahender Reddy Marri、Srujana Kodumuri、Durgaiah Chevella、Prabhakar Sripadi、Narender Nama
DOI:10.1039/c5ra16826k
日期:——
salt and oxone is reported. The preliminary mechanistic investigations suggest that the key factor for achieving the anti-Markovnikov regioselectivity is the semipinacol rearrangement of an iodo functionalized intermediate, which is confirmed by an isotope labeling experiment. In addition, the reaction involves the de-iodination of a co-iodo intermediate via its oxidation to hypervalent iodine species
Synthesis of <i>gem</i>-Difluoroalkenes via Nickel-Catalyzed Reductive C–F and C–O Bond Cleavage
作者:Zhiyang Lin、Yun Lan、Chuan Wang
DOI:10.1021/acscatal.8b04348
日期:2019.1.4
By merging C–O and C–F bondcleavage in cross-electrophile coupling, we developed a method for efficient synthesis of gem-difluoroalkenes with an alkoxy-substituent on the homoallylic position using easily accessible acetals as coupling partners with α-trifluoromethyl alkenes. Remarkably, this Ni-catalyzed allylic defluorinative cross-coupling reaction demonstrates high tolerance of a wide range of