497968-19-1Relevant articles and documents
Triethylborane induced radical reaction of gallium enolates with α-halo esters
Usugi, Shin-ichi,Yorimitsu, Hideki,Shinokubo, Hiroshi,Oshima, Koichiro
, p. 2049 - 2052 (2002)
Treatment of silyl enolates with methyllithium followed by an addition of gallium trichloride afforded the corresponding gallium enolates. The reaction of the resulting gallium enolates with α-halo carbonyl compounds in the presence of triethylborane as a radical initiator provided 1,4-dicarbonyl compounds in good yields.
Transition Metal-Free Reduction of Activated Alkenes Using a Living Microorganism
Brewster, Richard C.,Suitor, Jack T.,Bennett, Adam W.,Wallace, Stephen
supporting information, p. 12409 - 12414 (2019/08/16)
Microorganisms can be programmed to perform chemical synthesis via metabolic engineering. However, despite an increasing interest in the use of de novo metabolic pathways and designer whole-cells for small molecule synthesis, the inherent synthetic capabilities of native microorganisms remain underexplored. Herein, we report the use of unmodified E. coli BL21(DE3) cells for the reduction of keto-acrylic compounds and apply this whole-cell biotransformation to the synthesis of aminolevulinic acid from a lignin-derived feedstock. The reduction reaction is rapid, chemo-, and enantioselective, occurs under mild conditions (37 °C, aqueous media), and requires no toxic transition metals or external reductants. This study demonstrates the remarkable promiscuity of central metabolism in bacterial cells and how these processes can be leveraged for synthetic chemistry without the need for genetic manipulation.
Why Cyclopropanation is not Involved in Photoinduced α-Alkylation of Ketones with Diazo Compounds
Rybicka-Jasińska, Katarzyna,Or?owska, Katarzyna,Karczewski, Maksymilian,Zawada, Katarzyna,Gryko, Dorota
supporting information, p. 6634 - 6642 (2019/01/04)
Diazo compounds are widely used reagents in organic synthesis. Direct photolysis leads to singlet carbenes whereas, in the presence of a photosensitizer, carbenes in the triplet state are generated. However, their reactivity under light irradiation remains poorly understood. Herein, we report photocatalytic, direct alkylation of enamines, generated from ketones, with diazo esters in the presence of free-base porphyrins acting as photoredox catalysts. Based on the experimental and theoretical studies, we propose a plausible mechanism involving generation of an enamine radical cation that subsequently reacts with diazo compounds giving the radical thus excluding the controversial cyclopropanation–ring opening pathway.
Enantioselective synthesis of angularly substituted 1-azabicylic rings: Coupled dynamic kinetic epimerization and chirality transfer
Aron, Zachary D.,Ito, Tatsuya,May, Tricia L.,Overman, Larry E.,Wang, Jocelyn
, p. 9929 - 9948 (2013/10/22)
A new strategy for enantioselective synthesis of azacyclic molecules in which dynamic kinetic equilibration of diastereomeric iminium ions precedes a stereochemistry-determining sigmatropic rearrangement is reported. The method is illustrated by the synthesis, in high enantiomeric purity (generally 95-99% ee), of a variety of 1-azabicyclic molecules containing angular allyl or 3-substituted 2-propenyl side chains adjacent to nitrogen and up to three stereogenic centers. In these products, the size of the carbocyclic ring is varied widely (5-12 membered); however, useful yields are obtained in forming 1-azabicyclic products containing only fused pyrrolidine and piperidine rings. Chirality transfer from substituents at carbons 1 and 2 of the 3-butenylamine fragment of the starting material is investigated, with methyl and phenyl substituents at the allylic position shown to provide exquisite stereocontrol (generally 98-99% chirality transfer). An attractive feature of the method is the ability to carry out the key transformation in the absence of solvent. Illustrated also is the high yielding conversion of four such products to a new family of bicyclic β-amino acids of high enantiomeric purity.
