125593-32-0Relevant academic research and scientific papers
Mechanistic studies on the cyclizatlon of (Z)-1,2,4-heptatrien-6-yne in methanol: A possible nonadiabatic thermal reaction
Cremeens, Matthew E.,Hughes, Thomas S.,Carpenter, Barry K.
, p. 6652 - 6661 (2005)
Myers et al. pyrolyzed (Z)-1,2,4-heptatrien-6-yne (1) in methanol at 100°C and observed benzylmethyl ether (2) as a major product and 2-phenylethanol (3) as a minor product. If a biradical intermediate, such as the open-shell singlet state of α,3-didehydrotoluene (4), was the only intermediate generated by the cyclization, then reaction with methanol might be expected to afford 2-phenylethanol as the principal product. The question that has been of interest since its first discovery is the origin of the principal product of the title reaction, benzylmethyl ether. This report considers three mechanisms for formation of the benzylmethyl ether: direct methanol participation in the cyclization of the reactant, partial ether formation from the biradical 4, or involvement of the closed-shell zwitterionic state of α,3-didehydrotoluene (5). A fourth mechanism, involving a cyclic allene intermediate, has been ruled out by earlier studies. In the present work, the first two mechanisms are ruled out by experiment and/or calculation. The remaining one, involving the zwitterion, is shown to be consistent with experimental and computational data only if a component of the reaction follows a nonadiabatic course.
Carbenes and the O-H Bond: Hydroxyalkyl-Substituted Arylcarbenes
Kirmse, Wolfgang,Kund, Klaus
, p. 2325 - 2332 (2007/10/02)
carbene (4), phenylcarbene (19), and carbene (30) have been generated by photolysis of tosylhydrazone or diazo precursors in protic solvents.These carbenes give cyclic ethers (7, 18, 33) competitively with insertion into O-H bonds of the solvent.For comparison, the analogous benzyl cations (9, 17, 31) have been generated by solvolysis or dediazoniation.The cations are more sensitive to structural variation than their carbenic counterparts: 9 does not undergo intramolecular nucleophilic substitution, in contrast to 17 and 31.These observations are explicable in terms of high barriers for rotation about aryl-cation bonds, as compared with low barriers for rotation about aryl-carbene bonds.Two major effects of the solvent (ROH) and of the base (RONa) on product formation may be distinguished: (i) protonation of the carbene (or of its precursors) in the more acidic media leads to predominantly cationic processes; (ii) deprotonation of the OH group under strongly basic conditions enhances the nucleophilicity of the oxygen, and also facilitates insertion into the α-C-H bonds of 30.
