共查询到20条相似文献,搜索用时 15 毫秒
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Powers DC Leber PA Gallagher SS Higgs AT McCullough LA Baldwin JE 《The Journal of organic chemistry》2007,72(1):187-194
At 300 degrees C, bicyclo[4.2.0]oct-2-ene (1) isomerizes to bicyclo[2.2.2]oct-2-ene (2) via a formal [1,3] sigmatropic carbon migration. Deuterium labels at C7 and C8 were employed to probe for two-centered stereomutation resulting from C1-C6 cleavage and for one-centered stereomutation resulting from C1-C8 cleavage, respectively. In addition, deuterium labeling allowed for the elucidation of the stereochemical preference of the [1,3] migration of 1 to 2. The two possible [1,3] carbon shift outcomes reflect a slight preference for migration with inversion rather than retention of stereochemistry; the si/sr product ratio is approximately 1.4. One-centered stereomutation is the dominant process in the thermal manifold of 1, with lesser amounts of fragmentation and [1,3] carbon migration processes being observed. All of these observations are consistent with a long-lived, conformationally promiscuous diradical intermediate. 相似文献
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Vladislav Yu. KorotaevAlexey Yu. Barkov Pavel A. SlepukhinMikhail I. Kodess Vyacheslav Ya. Sosnovskikh 《Tetrahedron letters》2011,52(23):3029-3032
A new type of ring-chain tautomerism, which consists of the reversible conversion of bicyclo[4.2.0]octane derivatives into trisubstituted enamines was found and studied by 1H NMR spectroscopy. The starting materials were prepared by the stereoselective reaction of (E)-3,3,3-trichloro-1-nitropropene with cyclohexanone enamines. 相似文献
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Maurice Brookhart Richard E. Dedmond B.F. Lewis 《Journal of organometallic chemistry》1974,72(2):239-245
It has been shown that bicyclo[5.1.0]-2,4-octadieneiron tricarbonyl undergoes thermal isomerization to bicyclo[4.2.0]-2,4-octadieneiron tricarbonyl. The first-order rate constant for this process at 120.6° was determined to be 1.8 X 10?5 s?1 which corresponds to ΔF3 = 31.8 kcal/mol. Gas chromatographic results coupled with a kinetic analysis very strongly suggest that 1,3,5-cyclooctatrieneiron tricarbonyl is an intermediate in this isomerization. Two plausible mechanisms are offered to explain this rearrangement. 相似文献
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Reaction of lithium enolates of simple ketones with (+/-)-phenyl vinyl sulfoxide has potential for the convergent construction of complex fused ring systems containing a bicyclo[n.2.0]alkan-1-ol. The formation of sulfinylbicyclo[4.2.0]octan-1-ols 1-3 from the lithium enolate of cyclohexanone with (+/-)-phenyl vinyl sulfoxide or (R)-(+)-p-tolyl vinyl sulfoxide 18 was used to probe the mode of this novel cyclization reaction. Using phenyl vinyl sulfoxide, variations in the reaction lighting and solvent were investigated, in conjunction with radical trapping (TEMPO) and isotope labeling (deuterium) experiments. Cyclization to form sulfinylbicyclooctanols 1-3 is likely to proceed via an intermediate that ring closes to the bicycloalkanol anion 11 and was presently favored by the use of solvents such as THF or DME. 相似文献
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The preparation of exo and endo bicyclo[4.2.1]nonen-(3)-ol-(2) (3) and (4), and the preparation of exo and endo bicyclo[4.2.1]nonanol-(2) (1) and (2) from 3,3-dihalotricyclo[4.2.1.02,4]nonyl derivatives is described. On the basis of the configuration of the allylic alkohols 3 and 4 the configuration of the saturated compounds 1 and 2 has been unequivocally determined. 相似文献
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The preparation of exo and endo bicyclo[4.2.1]nonen-(2)-ol-(4) (3) and (4), and the preparation of exo and endo bicyclo[4.2.1]nonanol-(3) (1) and (2) from 3,3-dihalotricyclo[4.2.1.02,4]nonenyl derivatives is described. On the basis of the configuration of the allylic alkohols 3 and 4 the configuration of the saturated compounds 1 and 2 has been unequivocally determined. 相似文献
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Ronald N. Warrener Ian W. McCay Richard Y.S. Tan Richard A. Russell 《Tetrahedron letters》1979,20(34):3183-3186
Two new crystalline bicyclo[4.2.0]octa-2,4,7-trienes have been prepared by photodecarbonylation of the appropriate tricyclo[4.2.1.02,5]nona-3,7-dien-9-ones and their structures confirmed by 13C-n.m.r. The title compounds all undergo thermal ring opening to cyclooctatetraenes, but photolysis is substituent dependent. 相似文献
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Reaction of bicyclo[4.2.0]octane-2,5-diones with trimethylsilyl iodide gave bicyclo[3.3.0]oct-1(5)-en-2-ones by a clean reductive rearrangement in good yields, providing a simple and effecient synthetic method for the enones. 相似文献
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Kiyomi Kakiuchi Koichi MinatoKen Tsutsumi Tsumoru MorimotoHideo Kurosawa 《Tetrahedron letters》2003,44(9):1963-1966
Radical ring-opening reactions of bicyclo[4.2.0]octanones, its C6 alkyl derivatives, and tricyclic ketones promoted by SmI2 gave cyclohexanones via fission of the external cyclobutane bond. The CO2Me, CN, and phenyl derivatives led to the production of the eight-membered ring compounds through cleavage of the central cyclobutane bond. Using this regioselective reaction, the synthesis of (±)-acorenone was achieved. 相似文献
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The simple refluxing of allenynes, having a phenylsulfonyl functionality on the allenyl group, in xylene (or mesitylene) without microwave irradiation resulted in the efficient formation of bicyclo[5.2.0]nona-1,7-dienes and bicyclo[4.2.0]octa-1,6-dienes in high yields. This method was shown to be successfully applicable to the first construction of bicyclo[6.2.0]deca-1,8-dienes. Construction of the corresponding oxa- and azabicyclo[m.2.0] frameworks could also be attained. This thermal ring-closing reaction involves the formal [2+2] cycloaddition in which the distal double bond of an allenyl moiety exclusively served as one of the pi-components regardless of the position of the phenysulfonyl functionality on the allenyl moiety. 相似文献
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The 7,8-epoxy-2,3,5,6-tetrakis(methylene) bicyclo[2.2.2]octane; synthesis and diels-alder reactivity
The preparation of 7,8-epoxy-2,3,5,6-tetrakis(methylene)bicyclo[2,2,2] octane (5) is described. Evidence for transannular interaction between the homoconjugated s-cis-butadiene functions in 5 is found in the UV absorption spectrum. The Diels-Alder addition of 5 to tetracyanoethylene (TCE) is syn-regioselective and leads to the monoaducts 16:17 (85:15). The dienes 16,17 are less reactive than 5 toward TCE. anti-regioselectivity (leading to exo-2, endo-3-bis(chloromethyl)-5,6-bis(methylene)-syn-7,8-epoxybicyclo[2.2.2]octaves (25) is observed in the double elimination of HCl from the syn-7,8-epoxy-exo-2,endo-3,exo-5,endo-6-tetrakis(chloromethyl)bicyclo[2.2.2]octane (11), precursor of 5. The structures of the regioisomers 16,17 were confirmed spectroscopically and chemically. Elimination of HCl from the chloromethyl groups in 26 (TCE adduct of 25) and HCN from the TCE adducts 16, 17 and 26 can be induced by CsF in DMF. 相似文献
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Minoru Isobe Supaporn NiyomchonChia-Yi Cheng Anuch Hasakunpaisarn 《Tetrahedron letters》2011,52(16):1847-1850
A sesterterpenoid solanoeclepin A (1) has a unique structure including a bicyclo[4.2.0]octane substructure, for which a new synthetic methodology is explored particularly to cyclize functionalized cyclobutane rings. An optically active (R)-carvone and a racemic cyclohexenone were each converted into the respective epoxyvinylsulfones, and then subjected to the heteroatom-directed conjugate addition (HADCA) by a lithium acetylide nucleophile. The intermediate carbanions from HADCA were used for the following epoxide opening reaction yielding the four-membered carbocyclic products. 相似文献