The formation of the 2-bicyclo[3.1.0]hexyl cation by deamination and solvolysis, and the effect of methyl substitution at C-5

Abstract

Deamination of endo-and exo-2-aminobicyclo[3.1 .O] hexanes (7) and (8) and solvolysis of the corresponding 2-chloro-compounds (1) and (2) yield very similar ratios of products showing the intervention of a common 2-cation. Rate studies of solvolysis of 2-substituted bicyclohexyl derivatives and some 5-methyl-substituted compounds indicate that the normal rate-enhancing effect of the cyclopropyl group is due to delocalisation of the symmetrical homoallyl type for endo-and exo-leaving groups. Deuterium scrambling from the 5-position was not observed in solvolysis of chlorides (1) and (2). Leeds LS2 9JT 1 Preliminary communication, P. R. Brook, R. M. Ellam, and A. S. Bloss, Chem. Cornm., 1968, 425. p. 1295; (d) see also M. Hanack and H. J. Schneider, Angew. Chem. Internat. Edn., 1967, 6, 666; (e) B. Capon, Quart. Rev., 1964, 18, 45. charge and the neighbouring cyclopropyl group. Z-Substituted bicyclo[3.1 .O]hexanes were readily accessible compounds for study.A recent report prompts publication now. Tosyl esters of the epimeric bicyclo[3.1 .O]hexan-2-01s (4) and (5) were found too reactive for convenient isolation.g The corresponding endo-(1) and exo-Z-chlorobicyclohexanes (Z), were then chosen, as g.1.c. techniques could be used for analysis and purification (although not without difficulty).Reduction of bicyclohexan-%one (3) with sodium borohydride gave a mixture of the epimeric 2-alcohols containing 93% eutdo-derivative (4) .7 This mixture on of work closely related to our own

Total Synthesis of the Kopsia lapidilecta Alkaloid (±)-Lapidilectine B

“…Formation of the Smalley cyclization precursor 16 began with known 4-benzyloxycyclohexanone 20 , which was converted to alkenyl triflate 21 through O -sulfonylation of the corresponding enolate with N -phenyltriflamide 16 in 72% yield (Scheme ). Alkenyl triflate 21 was transformed into alkenyl stannane 19 with use of Wulff's palladium-catalyzed stannylation protocol .…”

Toward Selective Reactions with CH Bonds: A Rationale for the Regio- and Stereochemistry of Dichlorocarbene Insertions into Cyclic Hydrocarbons

“…Indeed, the results correlate well with the stability of the corresponding bicyclo[3.1.0]hexanyl cations obtained experimentally. The most stable bicyclo[3.1.0]hexanyl cation is the cyclopropyl carbinyl 1 + 2 (Figure ), because of an efficient delocalization of the positive charge by the three-membered ring . Other carbocations are only poorly stabilized …”

“…The most stable bicyclo[3.1.0]hexanyl cation is the cyclopropyl carbinyl 1 + 2 (Figure ), because of an efficient delocalization of the positive charge by the three-membered ring . Other carbocations are only poorly stabilized 2 Geometries of the transition states of the insertion of dichlorocarbene into 1 and 2 as given by B3LYP/6-31G(d) calculations.…”

Biogenetic-Type Rearrangements of Terpenes

“…However, deamination of cyclohex-3-enyl amine and solvolysis cyclohex-3-enyl tosylate gives exo-and endo-bicyclo[3.1.0]hex-2-yl derivatives as 6-43% of the products resulting from nucleophilic capture (101,103,104). The modest yield of bicyclic products in these reactions apparently is the result of competing nucleophilic capture prior to cyclization and hydride shift to the 2-cyclohexenyl cation.…”

“…BISARYA and DEV have examined the hydrolysis of allohimachalyl tosylate (101-0Ts) a reaction of obvious biogenetic significance (157). The stereochemistry of the nucleophilic capture of the intermediate carbonium ion in this solvolysis is apparently exactly the same as in the biosynthesis since the only alcohol products are himachalol (101-0H) and allohimachalol (103). The naturally occurring sesquiterpenes cx-and ß-himachalene (108 and 109) are also formed.…”