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131.
In the presence of AlBr3 in CS2 at temperatures below 0°, syn-tricyclo[4.2.1.12,5]decane ( 1 ) isomerizes exclusively to anti-tricyclo[4.2.1.12,5]decane ( 2 ) at a higher rate than the latter rearranges to 2-exo,3-exo-trimethylene-8,9,10-trinorbornane ( 4 ). However, at temperature above 0°, the anti-isomer 2 isomerizes to 4 faster than 1 to 2 and 4 . As a consequence, hydride abstraction occurs at C(3) (→carbocation a , which rearranges to carbocation b (anti-skeleton)) in the syn-isomer 1 , and more readily at C(9) (→carbocation c ) than at C(3) (→carbocation b ) in the anti-isomer 2 . 相似文献
132.
Tricyclic olefinic alcohols containing an unsymmetrically alkyl-substituted C, C-double bond were cyclized intramolecularly to their corresponding ethers under basic conditions: 9 → 12 , 10 → 17 + 18 , and 11 → 12 (Scheme 3, Table 1). The reactivity is mainly due to relieve of ground state strain. Alcohol 9 (endocyclic double bond) isomerized under intramolecular assistance by the hydroxyl group to 11 (exocyclic double bond) before cyclization to 12 occurred (Scheme 5). The latter step being the faster one, no isomerization 11 → 9 was observed. 相似文献
133.
2-Aza-7-thia-isotwistanes . 2-Aza-7-thia-isotwistanes were synthesized either starting from suitable 9-thiabicyclo[3.3.1]nonenes by olefin-amination ( 1 → 4 , 2 → 5 , 3 → 6 , 8 → 10 and 9 → 11 ) as well as by intramolecular substitution ( 25 → 26 ) or by molecular rearrangement starting from twistanes ( 21 → 19 and 22 → 10 ). From the isotwistanes thus obtained several other compounds ( 7 , 12 – 18 , 20 , 23 and 24 ) were prepared, too. 相似文献
134.
Photolysis of Bicyclo[3.3.1]nonan-2-one. Disproportionations, the secondary processes available to the acyl-alkyl biradical b (X(9) = 0) formed from 9-oxabicyclo[3.3.1]-nonan-2-ones a (X(9) = 0) in a primary photochemical process by α-cleavage (Norrish type I cleavage) were studied. Special attention was paid to the selectivity between the two possible H-abstractions: the one at C(3) (→ ketene c , X(9)= 0) and the other one at C(8) (→ alkenal d , X(9) = 0) and to the selectivity of the H-abstraction at a definite methylene group (C(3) or C(8)). In the case of ketene formation (→ c , X(9) = 0) the specificity of the insertion of the migrating H-atom at C(1) was studied. endo-6-Hydroxy-9-oxabicyclo[3.3.1]nonan-2-one ( 6 ) and derivatives of it ( 7, 8, 16, 17, 19, 21, 30 and 38 ) as well as exo-6-hydroxy-9-oxabicyclo[3.3.1]-nonan-2-one ( 41 ) and its derivative 42 were used as substrates. UV.-irradiation of 6 in benzene yielded 1,5-dioxa-2-cis-decalone ( 44 ) by way of a ketene g (R = H) as demonstrated by the photolysis of 7 (→ 45 ), 8 (→ 43 ), and 17 (→ 47 ). Specific labellings with deuterium proved that H-abstraction occurs intramolecularly at C(3) (e.g. 16 → 54 ; 6 + 16 → 44 + 54 ), that one of the H-atoms at C(3) migrates specifically to C(1) ( 21 → 55 ; 19 → 56 ), endo-H–C(3) being favored by a factor of 6. The abstraction showed an unexpected primary isotope effect of about 2. UV-irradiation of 41 in benzene yielded in addition to the expected 1,5-dioxa-2-trans-clecalone ( 63 ) about 3% of an isomeric compound 67 which probably results from H-abstraction at C(8) (→ alkenal 65) followed by cyclisation. 相似文献
135.
A synthesis of tricyclo [4.2.2.22,5]dodecane ( 19 ), a novel tricyclic C12H20 compound, is described. The key intermediate ketone 13 was prepared either from the C10-photodimer 1 of cyclopentadienone or the C11-cycloaddition products 11 and 12 . 13 was also transformed to tricyclo [4.2.2.12,5]undecane ( 8 ). 相似文献
136.
The synthesis of 2-oxa-6-aza-adamantane ( 21 ) and several of its derivatives ( 13–20 , 22 , 23 , 25–34 , 37 , and 38 ) was achieved starting from the 9-azabicyclo[3.3.1]nona-2,6- dienes 2 , and 3 , and 9-oxabicyclo[3.3.1]nona-2,6-diene ( 1 ). 相似文献
137.
Sippl W Contreras JM Parrot I Rival YM Wermuth CG 《Journal of computer-aided molecular design》2001,15(5):395-410
The paper describes the construction, validation and application of a structure-based 3D QSAR model of novel acetylcholinesterase (AChE) inhibitors. Initial use was made of four X-ray structures of AChE complexed with small, non-specific inhibitors to create a model of the binding of recently developed aminopyridazine derivatives. Combined automated and manual docking methods were applied to dock the co-crystallized inhibitors into the binding pocket. Validation of the modelling process was achieved by comparing the predicted enzyme-bound conformation with the known conformation in the X-ray structure. The successful prediction of the binding conformation of the known inhibitors gave confidence that we could use our model to evaluate the binding conformation of the aminopyridazine compounds. The alignment of 42 aminopyridazine compounds derived by the docking procedure was taken as the basis for a 3D QSAR analysis applying the GRID/GOLPE method. A model of high quality was obtained using the GRID water probe, as confirmed by the cross-validation method (q2
LOO=0.937, q2
L50% O=0.910). The validated model, together with the information obtained from the calculated AChE-inhibitor complexes, were considered for the design of novel compounds. Seven designed inhibitors which were synthesized and tested were shown to be highly active. After performing our modelling study the X-ray structure of AChE complexed with donepezil, an inhibitor structurally related to the developed aminopyirdazines, has been made available. The good agreement found between the predicted binding conformation of the aminopyridazines and the one observed for donepezil in the crystal structure further supports our developed model. 相似文献
138.
The synthesis of several derivatives of 2-oxa-7-aza-isotwistane ( 20–29 and 35 ) and 2-oxa-7-twistane ( 30–34 ) is described starting from cis,cis-cycloocta-1, 5-diene ( 1 ). The bicyclic acetoxy-olefin 10 was used as a key intermediate. The 10N(7)-isotwistane 22 was treated under reaction conditions suitable for molecular rearrangements involving an oxonium ion g , by neighbouring group participation, leading to 2-oxa-7-aza-twistanes. 相似文献
139.
[reaction: see text] Sulfonimidamides lead efficiently to nitrenes and have been converted to sulfimides, sulfoximines, and aziridines in good yields, through a copper-mediated multicomponent reaction. The stereogenic sulfur atom and the trivalent nitrogen atom present in the molecules open the way to asymmetric synthesis, whose first results are presented. 相似文献
140.
Rearrangements of 4,8-disubstituted 2,6-dioxa- and 2-oxa-6-aza-adamantanes to 4,10-disubstituted 2,7-dioxa- and 2-oxa-7-aza-isotwistanes as well as -twistanes. Substitutions and rearrangements involving neighboring group participation starting from 4,8-diiodo-2,6-dioxa- and 4,8-diiodo-2-oxa-6-aza-adamantanes ( 5 and 6, 12 and 48 , resp.) were studied, yielding 4,8-disubstituted 2,6-dioxa- and 2-oxa-6-aza-adamantanes ( 7, 9, 39, 42 and 13, 15, 50, 52 , resp.), 4,10-disubstituted 2,7-dioxa- and 2-oxa-7-aza-isotwistanes ( 8, 10, 41, 43 and 14, 16, 51, 53 , resp.) and corresponding-twistanes ( 11 and 17 , resp.). 相似文献