Bicyclo nona-3,5-diene

Thus the conversion of cis-6, 9 dimethylspiro [4, 4] nona-1, 3 diene to dimethyl bicyclo nona-diene is an example. The first product is a suprafacial [1, 5] carbon shift with retention of configuration at the migrating carbon. This is then followed by a [1, 5] hydrogen shift which becomes the major product. 

Silver trifluoroacetate is used in a one step synthesis of bicyclo[3 2 2]nona-6,8-diene-3-one from 2-methoxyallyl bromide and benzene [50] (equation 23) Analogous reactions of toluene, p-xylene, and mesitylene yield the corre spending substituted bicyclo[3 2 2]noiia-6,8-diene-3-ones [50]... 

An improved procedure59,60 uses bicyclo[3.3.1]nona-2,6-diene (39) instead of dione 31. Addition of N.JV-dibromo-p-toluenesulfonamide to 39 gives 40 which is debrominated to 41 and hydrolyzed to 2. 

Recent studies on iodination and iodochlorination of bicyclo[4.3.0]nona-3,7-diene (78) and its derivatives have shown that the reactions depend strongly on the presence and position of the methyl groups on the cyclohexene double bond and on reaction conditions. When I2 reacted with c/s-bicyclo[4.3.0]nona-3,7-diene the only product was endo-d-fcw-S-diiodobrexane84. The addition of IC1 or IBr to the same diene gives exclusively unrearranged products in an identical conformation, with the substituents in the six-membered ring in fraws-diequatorial position (equation 78)85. 

By comparison, the direction of halogenation of monomethyl-substituted bicyclo[4.3.0] nona-3,7-dienes depends" considerably on the position of the methyl group. For a diene lacking a substituent at C(3), the reaction proceeds with retention of the initial structure (equation 83), whereas in the case of the 3-methyl substituted diene, it occurs through transannular cyclization giving a brexane type monoiodo derivative (equation 84). 

Also, the structure of 63 is better described as zwitterionic with a C-N bond length of only 1.651 A <2001J(P2)133> in the case of methoxy instead of NMe2, the MeO- C=S separation is longer (2.550 A) and the two substituents behave as normal /rm-substituents. Furthermore, the 2,6,9-trioxo-bicyclo[3,3,l]nona-3,7-diene moiety 64 has been structurally characterized as part of Pd(ii) complexes <2003JOM(676)93> and as a novel chiral spacer unit in macrocyclic polyethers <2002SMC383, 2004T2857>. 

Another variation of valence isomerization of hexa-1,5-dienes is the [3,3] sigmatropic shift of a C — C bond (Cope rearrangement). Tor example, r/.v-bicyclo[6.1.0]nona-2,6-diene (27) isomer-izes at 60 C in one hour to give < /.v-bicyclo[5.2.0]nona-2,5-diene (28).73... 

Heteroanalogs of bicyclo[6.1.0]nona-2,6-dienes give, for example, 4-oxabicyclo[5.2.0]nona-2,5-dienc (31) and ethyl 4-azabicyclo[5.2.0]nona-2,5-diene-4-carboxylale (32) upon thermal isomerization.75... 

Chloroplatinate(II) salts can be used to prepare diene complexes of platinum(II), e.g. PtCl2(Ci2H18) from Dewar hexamethylbenzene,650,651 and PtCl2(diene)2 from 4-vinylcyclohexene, 1,4-cyclohexadiene, cis, cis-1,4-cyclononadiene, bicyclo[3.3. l]nona-2,6-diene and methylenecyclopentene.652-656... 

Similar geometric optimization has been reported for bicyclo[3.2.2]nona-6,8-diene (BND). The double bond situated in the opposite direction to the methylene group was found to be more exo-pyramidalized than the other double bond and the electron density (qi, HOMO) of the former double bond in HOMO of the molecule higher than that of the latter double bond. The exo and endo faces of exo-pyramidalized double bonds proved not to be equal and the electron density was found to be higher on the endo faces. The endo molecular complexes with bromine have been found by the HF/321G method to be more stable than their exo congeners this was attributed to electronic and steric factors. As a result, endo-facial stereoselectivity of bromination ( ) predominates.21 A related theoretical study of facial selectivity and regioselectivity of the electrophilic addition of chlorine to exo-tricyclo[4.2.1.02,5]nona-3,7-diene (exo-TND) has also been reported.22... 

Full geometric optimization of bicyclo[3.2.2]nona-6,8-diene (BND) based on semiempirical and ab initio methods has revealed that the double bond situated in the... 

The irradiation of 8-thia-l-aza-bicyclo[4.2.1]nona-2,4-diene 8,8-dioxide 125 with 350nm ultraviolet (IJV) light in pure acetone resulted in the formation of 2-thia-6-aza-tricyclo[5.2.0.01,4]non-8-ene 2,2-dioxide 60 in 52% yield <20040L1313>. However, photopolymerization occurred as a side reaction, but this can be prevented by the use of acetone with acetonitrile (2 1) as a solvent, although the yield diminished significantly to 28%. The authors proposed a mechanism for this reaction (Scheme 20) <20040L1313>. 

In contrast, thermolysis of 75 at 150 °C for 10.5 h afforded predominantly bicyclo[3,2,2]nona-6,8-diene 76 (95% yield) (Equation 13). In this case also, no tetracyclic product was detected. 

A preference for the coordination of an exocyclic C=C double bond in place of an endocyclic one was also observed for 9-methylene-bicyclo[4.2.1]nona-2,4,7-triene. With 55 this hydrocarbon forms [Cr(CO)3-(fj4 2-C10H10)], in which comparable stereochemistry with 56a is found. However, the diene portion shows Cr—C distances of 220 and 240 pm, as does the exocyclic C=C-double bond (80,81). Hence the differences of bond strengths are not as pronounced as in 56a. 

Tellurabicyclo[3.3. l]nona-2,6-diene, prepared from sodium tclluride and 1,5-dibromoocta-2,6-diene, lost tellurium when heated at 175° in toluene in a sealed tube giving bicyclo[5.1.0]octa-2,5-diene1. 

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