Posted by naturalproductman on February 4, 2016
When I think of organocatalysis, I usually think of a carbonyl compound forming an enamine intermediate, which in turn attacks an electrophile. The enamine is usually formed when the carbonyl compound reacts with a proline-derived catalyst. By using Gaussian and experimental KIE calculations, Matthew Vetticatt and co-workers at Binghamton University reported in JACS on the way that the enamine compound is formed: through an oxazolidinone intermediate.
A review article on determining the transition state structures based on KIEs.
Posted in Computational, Isotope effects, Mechanistic | Leave a Comment »
Posted by naturalproductman on January 28, 2016
Srinivasan Chandrasekaran and colleague at the Indian Institute of Science have reported in Tetrahedron on a mechanistically interesting transformation involving a geminal aminooxygenation of a vinyl arene. Two different reaction conditions were identified: one with m-CPBA, the other with a hypervalent iodine reagent. The former underwent a deuterium shift on the gem-dideuterated-styrene starting material and the latter does not.
Posted in Cascade Reactions, Hypervalent Iodine, Mechanistic, Methodology | Leave a Comment »
Posted by naturalproductman on October 16, 2015
Leadlay (University of Cambridge) and Sun (Wuhan University) and co-workers have reported in Chemical Science on thiotetronate biosynthesis.
Chemical Science paper
Posted in Biosynthesis, Mechanistic, Thiotetronate | Leave a Comment »
Posted by naturalproductman on October 5, 2015
David Collum and colleague have reported in JACS on the solution structure of an Evans enolate.
Posted in Computational, DFT, Mechanistic, Methodology | Leave a Comment »
Posted by naturalproductman on October 1, 2015
Kendall Houk and co-workers reported in JACS on a mechanistic investigation on a reaction discovered by Tius: the asymmetric Nazarov cyclization catalyzed by a thiourea-primary amine catalyst.
Posted in Computational, DFT, Mechanistic, Named Reactions, Nazarov cyclization | Leave a Comment »
Posted by naturalproductman on September 25, 2015
Peter Leadlay and co-workers from the University of Cambridge have reported in ACIE on the enzyme that makes the tetrahydropyran ring in salinomycin. The tetrahydropyran is proposed to come from a diol where one of the hydroxy groups is in the beta-position to a ketone and subsequently dehydrates to form an enone. The enone undergoes an intramolecular Michael reaction to form the tetrahydropyran. However, when the reaction is done in vitro with the purified enzyme, they don’t see the enone intermediate, so I wonder if it is a processive reaction; in other words, the enone forms in the enzyme active site without being released and cyclizes to the tetrahydropyran.
Posted in Biosynthesis, Chemical Biology, Enzymes, Mechanistic, Polyketides, Tetrahydropyran | Leave a Comment »
Posted by naturalproductman on September 4, 2015
Miguel Garcia-Garibay and co-workers at UCLA have reported in Organic Letters on a denitrogenation reaction of a triazoline using light to make an aziridine.
Posted in Computational, Light Mediated, Mechanistic, Methodology | Leave a Comment »
Posted by naturalproductman on July 13, 2015
Hafize Ozcan and co-workers from Trakya University in Turkey have reported in Tetrahedron on an interesting mechanistic investigation of the Newman-Kwart reaction.
Posted in Cascade Reactions, Computational, DFT, Electrocyclization, Mechanistic, Methodology, Named Reactions, Newman-Kwart, Sigmatropic Rearrangements | Leave a Comment »
Posted by naturalproductman on June 9, 2015
Ulrich Koert and co-workers from Philipps-University Marburg have reported in Organic Letters on an alpha-ketol rearrangment.They heat the reaction in a sealed tube to 70 degrees and the solvent is in DCM – with 2.5 mol equivalents of BF3 etherate, sounds a bit harsh – but nonetheless an interesting sigmatropic rearrangement.
Posted in Cascade Reactions, Mechanistic, Methodology | Leave a Comment »