Addition initiated ring closure substituted spiro[4,2]Hepta-1,3-dienes via fulvene intermediates
作者:Kazimierz Antczak、John F. Kingston、Alex G. Fallis
DOI:10.1016/s0040-4039(01)81165-5
日期:1984.1
The reactivity of the epoxy-fulvene 1 with various nucleophiles has been examined. It is a versatile Intermediate for the preparation of spiro[4.2]hepta-1,3-diene synthons via nucleophilic addition to the C6 position followed by intramolecular cyclization of the substituted cyclopentadiene anion generated in situ.
Regioselective control of allyl anions with cadmium chloride: α γ condensation with aldehydes
作者:Lei Bo、Alex G Fallis
DOI:10.1016/s0040-4039(00)85166-7
日期:1986.1
A general method for directing the condensation of allyl anions such as with aldehydes preferentially to the γ position of the unsaturated nucleophile is described. The procedure employs cadmium chloride to control the regioselectivity and will facilitate the extended use of vinylogous anions in synthesis.
Antczak, Kazimierz; Kingston, John F.; Fallis, Alex G., Canadian Journal of Chemistry, 1984, vol. 62, p. 2451 - 2455
作者:Antczak, Kazimierz、Kingston, John F.、Fallis, Alex G.
DOI:——
日期:——
Lei, Bo; Fallis, Alex G., Canadian Journal of Chemistry, 1991, vol. 69, # 9, p. 1450 - 1456
作者:Lei, Bo、Fallis, Alex G.
DOI:——
日期:——
Cycloaddition routes to tricyclo[5.4.01,7.02,9]undecanes: a direct total synthesis of (+)-longifolene via an intramolecular Diels-Alder strategy
作者:Bo Lei、Alex G. Fallis
DOI:10.1021/jo00060a039
日期:1993.4
The total synthesis of the sesquiterpene (+)-longifolene (1) by an intramolecular Diels-Alder cycloaddition strategy is described. Addition of methyllithium to the epoxyfulvene 13, derived from cyclopentadiene and 3,4-epoxy-2-butanone, led to an exo-tet cyclization of the resulting cyclopentadienyl anion to generate the spiro[2.4]hepta-4,6-diene alcohol 14. Resolution of this material was effected via its menthyl carbonate derivative 15. Oxidation of the (+)-R-alcohol with active MnO2 afforded the cyclopropyl aldehyde 16 which was condensed with the anion derived from methyl 3-methylcrotonate in the presence of cadmium chloride to generate the unsaturated lactone 20 or the unsaturated ester 18. Microwave heating of the silyl triene 19 effected cycloaddition to the adduct 21. Hydrogenolysis of the alcohol 22 afforded the ''sinularene'' skeleton 25. Cyclopropane ring cleavage of the derived ketones 23, 30, and the thiocarbonate 27 was examined but only in the Li/NH3 reduction of 30 was the longifolene skeleton 33 produced as a significant product which unfortunately could not be separated from its isomer 32. Consequently the successful route utilized regiospecific cleavage of the cyclopropane ring in the cyclopentadiene 20 in methanol catalyzed by BF3.Et2O to afford the substituted cyclopentadiene lactone(s) 34 (83%). Cyclization proceeded smoothly, in a sealed tube, in toluene, in a microwave oven to afford the single tetracyclic adduct 39 in 97 % yield. Double bond hydrogenation and reduction of the lactone with LiAlH4 afforded the substituted longifolene skeleton, and the resulting primary alcohol was acetylated selectively to give 40. Free-radical-mediated replacement of the secondary oxygen functions was accomplished via the phenoxythiocarbonate derivative to afford the methoxy acetate 43. Alternatively the reaction sequence could be modified to convert 39 to 41 to 42 and then to 43. Methoxy cleavage (Me3SiI) and a second free-radical reaction gave the acetate 44. Pyrolysis of this acetate (525-degrees-C) provided (+)-longifolene (1).