60788-55-8Relevant academic research and scientific papers
Chemo-, regio-, and diastereoselective synthesis of functionalized cyclopropanes by cyclization of dilithiated nitriles with epibromohydrin
Langer, Peter,Freifeld, Ilia
, p. 3903 - 3905 (2001)
MATRIX PRESENTED The cyclization of 1,1-dianions with epibromohydrin results in chemo-, regio-, and diastereoselective formation of functionalized hydroxymethyl cyclopropanes.
Conformational restriction by repulsion between adjacent substituents on a cyclopropane ring: Design and enantioselective synthesis of 1-phenyl-2-(1-aminoalkyl)-N,N-diethylcyclopropanecarboxamides as potent NMDA receptor antagonists
Shuto, Satoshi,Ono, Shizuka,Hase, Yukako,Kamiyama, Noriko,Takada, Hironao,Yamasihita, Kanako,Matsuda, Akira
, p. 915 - 923 (2007/10/03)
Adjacent substituents on a cyclopropane ring mutually exert steric repulsion quite significantly, because they are fixed in eclipsed conformation to each other. Based on this structural feature of the cyclopropane ring, conformationally restricted analogs of milnacipran (1), namely 1-phenyl-2-(1-aminoalkyl)-N,N-diethylcyclopropanecarboxamides (2, 3, ent-2, and ent-3) were designed as potent NMDA receptor antagonists and were synthesized highly enantioselectively. Reaction of (R)-epichlorohydrin [(R)-5] and phenylacetonitrile (6) in the presence of NaNH2 in benzene gave a chiral cyclopropane derivative that was isolated as lactone 4 with 96% ee in 67% yield, after alkaline hydrolysis of the cyano group. The nucleophilic addition reaction of Grignard reagents to aldehyde 10, which was readily prepared from 4, proceeded highly selectively from the si-face to afford addition products 11 in high yields. Although hydride reduction of the corresponding ketone 15b, prepared from 11b, with L-Selectride also proceeded highly diastereoselectively, the facial selectivity was reversed to give the re-face addition product lib. On the other hand, reduction of 15 with DIBAL-H afforded the si-face addition product 12 in high yields. These results suggested that these nucleophilic addition reactions proceeded via either the bisected s-trans or s-cis conformation of the cyclopropylcarbonyl derivatives. From 11 and 12, the target conformationally resticted analogs, 2 and 3, were synthesized, respectively. Starting from (S)-epichlorohydrin [(S)-5], their corresponding enantiomers, ent-2 and ent-3, were also synthesized. The structures of the conformationally restricted analogs detected by the X-ray crystallographic analysis suggested that their conformations can be restricted as we hypothesized. Thus, a new method for restricting the conformation of cyclopropane derivatives has been developed.
Elimination and Addition Reactions. Part 41. Nucleophilic Eliminative Fission of Cyclopropanes: the Coiled Spring Effect of Ring Strain on Nucleofugality and its Evaluation
Hughes, Simon,Griffiths, Gwerydd,Stirling, Charles J. M.
, p. 1253 - 1264 (2007/10/02)
Rates have been measured of sulphonyl-activated eliminative ring fissions of a series of six cyclopropanes in which the leaving group is stabilised by alkoxycarbonyl, cyano, or sulphonyl groups.The measurements allow assignment of ranks (nucleofugalities) to carbon leaving groups in systems in which the connection to the leaving group is strained by incorporation in a cyclopropane ring.The values obtained are compered with those obtained for a unstrained (acyclic) analogues.Rank enhancements of about 9(log) units are obtained; these enhancements suggests that free energies of activation for leaving-group expulsion are reduced by about 53 kJmol-1, or about 46 percent of these excess of enthalpy of the strained ring, notwithstanding the small degree of ring fission in the transition structure.The effect of phenyl substitution at the leaving group suggests that cleavage of the ring is very little advanced in the transition structure, although this is variable with the nature of the leaving-group stabilisation.This is the first direct determination of the effect of strain on nucleofugality.
