The Reactions of Some Barbituric Acid Derivatives in Concentrated Sulfuric Acid<sup>1</sup>
作者:E. W. Maynert、Elizabeth Washburn
DOI:10.1021/ja01099a055
日期:1953.2
Certain dialkylbarbituric acids are subject to dealkylation in sulfuric acid. resonance in the barbituricacid ring and the relative stabilities of the dislodged carbonium ions. thiobarbituric acids rearrange in sulfuric acid to yield 2-alkylthio derivatives. acid ring is cleaved, whereas an allyl group may be readily converted to the 2-hydroxypropyl derivative. acid is transformed into the dilactone
Triflic Acid Mediated Dealkylative Lactonisation via NMR-Observable Alkyloxonium Intermediates
作者:M. Paz Muñoz、Guy C. Lloyd-Jones
DOI:10.1002/ejoc.200800970
日期:2009.2
self-catalysed reaction with the pent-4-enoate to generate an oxonium triflate intermediate (rate ˜ kobsd.[TfOH]2[ester]1), possibly via the dimer (TfOH)2. The oxonium triflate intermediate then evolves to the ?-lactone according to unimolecular kinetics, liberating MeOTf in an SNi reaction. 2H-labelling experiments with TfOD suggest that the acid protonates the carbonyl moiety of the ester, with subsequent intramolecular
Phosphinite Ligand Effects in Palladium(II)-Catalysed Cycloisomerisation of 1,6-Dienes: Bicyclo[3.2.0]heptanyl Diphosphinite (B[3.2.0]DPO) Ligands Exhibit Flexible Bite Angles, an Effect Derived from Conformational Changes (exo- orendo-Envelope) in the Bicyclic Ligand Scaffold
作者:Ian J. S. Fairlamb、Stephanie Grant、Simona Tommasi、Jason M. Lynam、Marco Bandini、Hao Dong、Zhenyang Lin、Adrian C. Whitwood
DOI:10.1002/adsc.200600346
日期:2006.11
Changes in bidentate ligand structure significantly affect catalytic activity in mono-cationic Pd(II)-catalysed 1,6-diene cycloisomerisation processes to give cyclopentene products. A bicyclo[3.2.0]heptanyl diphosphiniteligand (B[3.2.0]DPO, 3) is the first phosphorus-based bidentate ligand capable of promoting regioselective 1,6-diene cycloisomerisation. Trace quantities of water are essential for
Copper-catalysed intramolecular O–H addition to unactivated alkenes
作者:Luis A. Adrio、Louisa Shuyi Quek、Jason G. Taylor、King Kuok (Mimi) Hii
DOI:10.1016/j.tet.2009.10.055
日期:2009.12
Intramolecular cyclisation of omega-alkenoic acids and alkenols can be achieved using a catalytic amount of Cu(OTf)(2) to afford lactones and cyclic ethers, offering a practical alternative to existing catalysts. (C) 2009 Elsevier Ltd. All rights reserved.