97487-36-0Relevant academic research and scientific papers
Vinyl Cations. 41. Influence of 4-Aryl and 4-Alkyl Substituents on the ?-Route Solvolyses of Homopropargyl Esters
Collins, Clair J.,Hanack, Michael,Stutz, Herbert,Auchter, Gerhard,Schoberth, Winfried
, p. 5260 - 5268 (1983)
The four 4-substituted-homopropargyl tosylates and triflates 6b-e (R=phenyl, p-tolyl, anisyl, and cyclopropyl) have been synthesized and solvolyzed under various conditions, as have 2-cyclopropyl-1-cyclobutenyl triflate (11-OTf) and nonaflate (11-ONf).In addition, the solvolyses of pent-3-yn-1-yl tosylate (6a-OTs, R=methyl) and triflate (prepared previously) are reported.The ratios of C-3 ring to C-4 ring 3 ring/C4ring)> products are recorded for the reactions in various solvents.As expected, ring closure (kΔ) increases and solvent displacement (kS, SN2) decreases with decreasing nucleophilicity of solvent.Temperature effects are noted for the sovolyses of tosylates 6a-e in 100percent TFE buffered with Na2CO3 in which kΔ increases with increasing temperature.The result is explained by decomposition of the intimate ion pair with temperature, whereupon elimination to the enyne becomes smaller and ring closure (kΔ) increases at the expense of elimination.The possibility of intervention of nonclassical vinyl cations is discussed, as are other mechanistic implications.
Solvolysis of 1-pent-3-ynyl triflate. Mechanism of the homopropargyl rearrangement
Hanack, Michael,Collins, Clair J.,Stutz,Benjamin, Ben M.
, p. 2356 - 2360 (2007/10/02)
1-Pent-3-ynyl triflate (1b) was solvolyzed (25°C, 24 h) in ethanol-water with 2,6-lutidine as the buffer. Products were formed predominantly (97-98.5%) through direct substitution (ks processes) and elimination. As the water content increases, the yields of 2-methylcyclobutanone (7b) (formed through kΔ processes) also increase from 0.2% (100% ethanol) to 2.8% (50% ethanol). 1-Pent-3-ynyl triflate was solvolyzed in anhydrous trifluoroethanol (25°C, 24 h) in nine different experiments with nine different buffers. Sodium and calcium carbonate, 2,6-lutidine, pyridine, and quinoline all favored kΔ processes (88-65%), whereas potassium carbonate, triethylamine, and sodium trifluoroethoxide suppressed the formation of rearranged products. The products of the solvolyses include: 2-methylcyclobutenyl trifluoroethyl ether (5b); cyclopropyl methyl ketone (6b); 2-methylcyclobutanone (7b); pent-1-en-3-yne (13); 1-pent-3-ynol (15); 2-methylcyclobutanone bis(trifluoroethyl) acetal (16), and 1-pent-3-ynyl trifluoroethyl ether (17). In 80% trifluoroethanol-20% water (sodium carbonate buffer) the yields of rearranged products (kΔ) dropped to 46% - as expected for an increase in nucleophilicity of the solvent. A quantitative correlation exists between percent rearrangement of 1b and nucleophilicity of the solvent, as demonstrated by use of the Winstein-Grunwald-Swain equation. 1-Pent-3-ynyl triflate was synthesized with carbon-14 in the 1 position (1b-1-14C) and, separately, in the 3 position (1b-3-14C). 1-Pent-3-ynyl triflate was also prepared doubly labeled both with carbon-14 and with deuterium (1b-3-14C-1,1-d2). Isotope effects were determined for all isotope position isomers. These are: k/*k = 1.048 ± 0.003 (1b-1-14C); k/*k = 0.990 ± 0.005 (1b-3-14C); and Hk/Dk = 1.098 ± 0.004 (1b-1,1-d2). In addition, 1b-1,1-d2 on solvolysis in trifluoroethanol-sodium carbonate yields 2-methylcyclobutanone (7b) containing equal fractions of 7b-3-d2 and 7b-4-d2. The tracer and isotope effect experiments confirm the mechanistic conclusions arrived at through product distribution studies and, in addition, offer strong evidence for significant anchimeric assistance during the kΔ processes investigated.
