197148-68-8Relevant academic research and scientific papers
Six- vs seven-membered ring formation from the 1- bicyclo[4.1.0]heptanylmethyl radical: Synthetic and ab initio studies
Kantorowski, Eric J.,Eisenberg, Shawn W. E.,Fink, William H.,Kurth, Mark J.
, p. 570 - 580 (1999)
The viability of utilizing 1-bicyclo[4.1.0]heptanylmethyl radical (3) to serve as a progenitor of seven-membered carbocycles was examined. Rate constants for the rearrangement of this radical to 3-methylenecycloheptyl radical (4) and 2-methylenecyclohexyl-1-methyl radical (6) were measured using the competition method of 3 with thiophenol over the temperature range of -75 to 59 °C. Arrhenius functions were calculated for the conversions of 3 to 4 and 3 to 6 and found to be log(k/s-1) = (12.38 ± 0.20) - (5.63 ± 0.23)/θ and log(k/s-1) = (11.54 ± 0.32) - (5.26 ± 0.37)/θ, respectively. The rate constants for these conversions at 25 °C are 1.86 x 108 s-1 and 5.11 x 107 s-1, respectively. Hence, the seven-membered ring-expanded carbocycle is formed 3.6 times faster at 25 °C than the nonexpanded species. This suggests that the 1-bicyclo[4.1.0]heptanylmethyl radical system may be synthetically useful in seven-membered ring-forming methodology. Preliminary theoretical examination of this radical system qualitatively predicted the experimentally determined energies of activation: PMP4/6-31G*//HF/6-31G*ΔE(a) (3 → 6 - 3 → 4) = 3.0 kcal/mol with zero point energy correction. The HF/6-31G* optimized reaction coordinate stationary points suggest cyclopropyl substituent eclipsing interactions play an important role in determining the kinetic outcome of these rearrangements.
Cyclization of Hindered Fluorinated Dichloro(5- And 6-)alkenyl Radicals. Structural Effects of Olefins on the Selective Formation of 5-exo and 6-endo Cyclization Products
Okano, Takashi,Ishihara, Hidemasa,Takakura, Nobuyuki,Tsuge, Hiroyasu,Eguchi, Shoji,Kimoto, Hiroshi
, p. 7192 - 7200 (2007/10/03)
Reaction of 3-butenyl radicals generated by photolysis of variously substituted Barton esters (both open-chain 1a-d and cyclohexyl 1e-h) with CF2=CCl2 gave a mixture of cyclized products (cyclopentanes 6 and 8 and cyclohexanes 7 and 9) as well as noncyclized products (4 and 5) in various ratios depending on the substitution pattern at the olefinic moiety. The product ratios of [cyclization (6 + 7 + 8 + 9):noncyclization (5)] for 1 with more alkyl substituents on the CC double bond were greater than those for 1 with fewer substituents. The products ratio of [5-exo (6 + 8): 6-endo (7 + 9)] was influenced by a steric effect. Photoreaction of Barton ester 2 with CF2=CCl2 gave a mixture of cyclohexanes 16 and 17 as well as noncyclized 14 and 15. Dehydrochlorination of decalins 7g and 7h followed by oxidation of sulfide and [2,3]sigmatropic rearrangement of the allyl sulfoxide gave octahydronaphthalenones 23 and 27, respectively.
