Tricyclo 6.2.2.0 dodecanes

The Diels-Alder dimerization of 2,6,6-trimethyl-2,4-cyclo-hexadienone to l,4,6,6,9,9-hexamethyl-A -tricyclo-[6.2.2.0 ]-dodecane-5,10-dione facilitates its separation from the major alkylation product, 2,6-dimethylanisole. 

On the other hand, Kibayashi [46] and Marazano [47] first prepared the diazabicyclo[3.3.1]nonane system and converted it to a 2,6-diaza-tricyclo[6.2.2.0 ]dodecane skeleton (37 and 41) by intramolecular alkylation or acylation. Bonjoch [48] also reported a synthesis of diazabicy-clo[3.3.1]nonane (50) by a palladium-mediated intramolecular coupUng reaction. It is still difficult to construct polyunsaturated 11- and 15-membered rings. 

Wahrend l-ChIor-6-oxo-3,3-dimethyI-cyclohexen bei -2,05 Vin wasserfreiem Aceto-nitril zum 6-Oxo-3,3-dimethyl-cyclohexen (66% d.Th.) reduziert wird, erhalt man in was-serhaltigem Acetonitril, ebenfalls bei -2,05 V, 2,12-Dichlor-l-hydroxy-3-oxo-6,6,9,9-tetramethyl-tricyclo[6.3.1.02 7]dodecan (18% d. Th.)2 ... 

Among bicyclic cyclohex-2-enones, the formation of tricyclo[4.4.2.01,6]dodecane-2,7-dione from bicyclo[4.4.0]dec-l(6)-ene-2,7-dione and ethene proceeds in 95% yield,101 and that of 8-mcthyl-tricyclo[6.4.0.01,4]dodecan-5-ones from 6-methylbicyclo[4.4.0]dec-l(2)-en-3-one and ethene in 77% yield,102 respectively. Steroids containing cyclohex-2-enone subunits,103 e.g. 17/ -acetoxy-5a-androst-1 -en-3-one,104 often afford /raw-fused cycloadducts with alkenes. When such reactions are performed on silica gel, complete reversal of stereochemistry to that observed in solution can occur.105... 

In the case of tricyclo[4.4.2.01-6]dodecan-2-one, acid-catalyzed rearrangement gave tricy-clo[4.3.3.01,6]dodecan-7-one (8), the propellane-like skeleton of which is otherwise difficult to construct synthetically. The reaction mechanism requires two consecutive Wagner-Meerwein... 

Fig. 3.71 Effect of addition of Eu(fod)3 on the chemical shift values for the protons in A, 7V -tfw efAy/-(7s,fr

Figure 11. Molecules that are chiral in the excited state only, (a) (lS,3R,7R,9S)-tricyclo-[7.3.0.03 7]dodecane-5,11 -dione in the electronic ground state, (RS), and in locally excited n ->Jt states, (.RS ) and (RS).5S (b) 3-(1nJt )-(lS,6R)-bicyclo[4.4.0.]decane-3,8-dione prepared by thermal decomposition of enantiopure 1,2-dioxetanes. 56...

Spiro 6.6 tridec-2-en 6-Oxo- E17c, 2595 (2-Acyl — 1-etheny] — cyclo-propan/Li —NR2 + R3Si —Cl) Tricyclo[4.4.2.0l6]dodecan 11 (or 12)-Methylen-2-oxo- E21c, 3104 (bicycl. En — on + Allen) Tricyclo 6.4.01 s]dodecan 8-Methyl-... 

With palladium(O) in the presence of phosphane ligands, the selectivity of the reaction is much lower. Besides 67% polymeric material, a 33% combined yield of cycloaddition products is obtained with a palladium/triphenylphosphane molar ratio of 1 1 after 2 hours at room temperature with complete conversion. The cycloaddition products consist of the dimer 30 (12%), methyl 3,3,7,7-tetramethoxy-exo-tricyclo[4.1.0.0 ]heptane-5-acetate (32, 71%) as the decomposition product of the primarily formed 5-(2,2-dimethoxyethenyl)-3,3,7,7-tetramethoxy-e.V( -tricyclo[4.1.0.0 ]heptane (31), and 3,3,6,6,9,9,12,12-octamethoxy-exo,enrfo,cxo-pentacyclo [9.1.0.0 . 0 . 0 i°]dodecane (33, 17%). 

Figure 7). Osawa s recent force-field calculation study (21) of cage-shaped molecules with ethano bridges affords an excellent demonstration of this twist deformation at the molecular level. In six achiral cage-shaped molecules so far studied, his calculations showed that each molecule assumed a twisted, chiral conformation to minimize torsional and nonbonding strain. Tricyclo[4.2.2.2.2,s]dodecane (5) was shown to be 1.1 kcal/mol more stable in a twisted D2 than in the eclipsed D2h conformation, and his calculation also suggests that perhydrotriquinacene and C16-hexaquinane should assume C3 rather than conformations, contrary to naive pictures obtained by a casual observation of molecular models. 

GeC>2 (0.60 g) was dissolved in 52.95 g of a 0.6M solution of l,3,3-lrimelhyl-6-azonium-tricyclo[3.2.1.46 6]dodecane hydroxide. Then, 12.60 g of tetraethyl orthosilicate and 0.27 g of aluminum isopropoxidc were added and left under stirring until the alcohol and the amount of water necessary to reach the final composition were evaporated. The final gel was homogenized and put into an autoclave for 18 days at 175 °C. After cooling down to room temperature, the solid phase was recovered by filtration and washed. Calcination was carried out in a stream of air at 540 °C for 3 h [9]. 

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