Hypervalent Iodine Oxidation of Allenes: Synthesis of 3-Acetoxy-3-alkoxypropynes, 2-Alkoxy-3-tosyloxypropanals and Phenyl-Substituted Propenals and Propenones
Highly Enantioselective Asymmetric Autocatalysis of Pyrimidin-5-yl Alkanol Induced by Chiral 1,3-Disubstituted Hydrocarbon Allenes
摘要:
1,3-Disubstituted chiral allenes without any heteroatoms act as chiral initiators in the addition of (i-Pr)(2)Zn to pyrimidine-5-carbaldehyde to afford. in combination with the subsequent asymmetric autocatalysis, chiral pyrimidin-5-yl alkanols with up to 98% ee. The absolute configuration of the pyrimidin-5-yl alkanol formed depend on that of the chiral allene.
An extremely short-lived 1,4-biradical as intermediate in the photo-cycloaddition reactions of triplet state aromatic thiones with allenes
作者:Johan Kamphuis、Hendrik J. T. Bos、Robert J. Visser、Bert H. Huizer、Cyril A. G. O. Varma
DOI:10.1039/p29860001867
日期:——
of the aromatic thione in the thermal reaction with an allene and log ka depend linearly on the ionization energy of the allene. Previous suggestions that the 1,4-biradical has a triplet state exciplex as precursor are rejected on the basis of the similarity of these relations and because of the fact that there is no difference in the effect on ka and kt caused by deuteriation of the allene.
Cobalt-Catalyzed C–H Activation and [3 + 2] Annulation with Allenes: Diastereoselective Synthesis of Indane Derivatives
作者:Arnab Dey、Chandra M. R. Volla
DOI:10.1021/acs.orglett.1c01521
日期:2021.7.2
ve [3 + 2] annulation reaction has been achieved, employing allenes as the annulation partners. The selective 2,3-migratory insertion of allenes with arylcobalt(III) species and the subsequent intramolecular diastereoselective nucleophilic addition of η1-allylcobalt onto the imine resulted in [3 + 2] annulation over the alternative [4 + 2] annulation. Furthermore, the oxidative annulation obviates
Kinetics and mechanism of gas-phase pyrolysis of ylides. Part 3.<sup>1</sup>Thermal reactivity of<i>α</i>-carbonyl- and thiocarbonyl-stabilized methylenetriphenylphosphoranes
作者:Rasha F. Al-Bashir、Nouria A. Al-Awadi、Osman M. E. El-Dusouqui
DOI:10.1002/poc.1752
日期:2011.4
Fourteen ketone/thione‐stabilized triphenylphosphonium methylides were subjected to conventional gas‐phase and flash vacuum pyrolysis (FVP). The kinetics of the first‐order thermal gas‐phase reactions of all these compounds were investigated over 360–653 K temperature range. The values of the Arrhenius log A and energy of activation of these ylides averaged 11.52 ± 0.34 s−1 and 133.20 ± 3.14 kJ mol−1
Samarium Diiodide-Induced Couplings of Carbonyl Compounds with Methoxyallene Leading to 4-Hydroxy 1-Enol Ethers
作者:Alexandra Hölemann、Hans-Ulrich Reissig
DOI:10.1021/ol0342251
日期:2003.5.1
A surprising samarium diiodide-induced coupling reaction of carbonylcompounds with methoxyallene provided 4-hydroxy 1-enol ethers, which are versatile synthetic building blocks. In this coupling reaction, methoxyallene serves as an acrolein equivalent, which cannot directly be employed. [reaction: see text]
Readily available phenol-derived biaryls reacted with allenes underpalladiumcatalysis to provide a variety of highly valuable spiro[cyclohexane-1,1′-indene]-2,5-dien-4-ones. This new catalytic process, involving a key step of regioselective allylative dearomatization of phenol, proceeded efficiently through a [3 + 2] spiroannulation pathway by overcoming undesired β-hydride elimination. Preliminary