182143-32-4Relevant academic research and scientific papers
Carbocationic n-endo-trig cyclizations
Shi, Lei,Horn, Markus,Kobayashi, Shinjiro,Mayr, Herbert
supporting information; experimental part, p. 8533 - 8541 (2010/03/26)
Unsaturated benzyl cations (4-MeOC6H4)CH +-(CH2)n-CH=CH2 (1) have been generated laser-flash photolytically in acetonitrile in the presence of enol ethers or 2-methylfuran. The reactions of the cations 1 (n = 2 and 4) with these π-nucleophiles follow second-order rate laws with rate constants comparable to those of the analogous saturated species (4MeOC6H 4)CH+-(CH2)3CH3. Product studies show the absence of cyclization products. In contrast, the carbocation (4-MeOC6H4)CH+-(CH2) 3-CH=CH2 (Id) undergoes a highly reversible 6endo-trig cyclization which is approximately 107 times faster than the corresponding intermolecular reaction of (4MeOC6H4)CH +-(CH2)3CH3 with hex1-ene. This cyclization yields a highly electrophilic, partially bridged carbocation, which accounts for the finding that Id is consumed eight times faster in trifluoroethanol solution than all other carbocations of this series. Quantum-chemical calculations (B3LYP/6311G(d,p) and MP2/6-31+G(2d,p)) have been performed to elucidate the structures of the involved carbocations. Consequences of these findings on the role of π-participation in solvolysis reactions are discussed.
Polar and steric substituent effects in 5-exo-trig cyclizations of 1-aryl-4-penten-1-oxyl radicals
Hartung, Jens,Hiller, Margit,Schmidt, Philipp
, p. 1425 - 1436 (2007/10/03)
A series of 1-aryl-substituted 4-penten-1-oxyl radicals 2 were generated from parent N-alkoxypyridinethiones 6. The intermediates 2 undergo 5-exo-trig cyclizations which are sensitive to polar and steric substituent effects. Thus, para groups in the aroma
