2-Bicyclo heptyl derivatives

Studies of the rates and products of hydrolysis of ewJo-and exo-2-bicyclo[4.1.0]heptyl derivatives 75 and 76 were first reported in preliminary form by Goering and Rubenstein and later in more detail by othersThe relative rates below for reactions in 80% aqueous acetone at 80°C reveal that as with the 2-bicyclo[3.1.0]hexyl system (fc[4.1.0] = ca.l50/c[3.1.0]) reaction rates are essentially independent of leaving group geometry. This indicates that both exo and endo isomers can ionize through bisected... 

Gassman and Creary besides studying the parent 2-bicyclo[4.1.0]heptyl derivatives 75 and 76, also examined the effects of introducing a 4,5-double bond as in 77 and 78. The relative rates given below were for p-nitrobenzoate hydrolysis in 70% acetone at 100°C, and... 

Finally, several systems which are more commonly thought of as dehydroadamantyl or dehydrohomoadamantyl systems may also be considered as 2-bicyclo[4.1.0]heptyl derivatives. For the case of the 8,9-dehydro-2-adamantyl 3,5-dinitrobenzoate (85),... 

In a subsequent calculational study [HF and MP2 levels of theory with 6-31G(d) basis set and MP4(SDQ)], Szabo and Cremer849 explored the he C7Hn+ potential energy surface. Cation 487 (tricyclo[4.1,0.01,3]heptyl cation), the protonated ethano-bridged derivative of spirocyclopentyl cation, was considered to be the missing link between the bicyclo[3.2.0]hept-3-yl cation 488 and the 7-norbomyl cation 489. It is a kinetically stabilized species separated from cations 488 and 489 by 18.9 and 15.9 kcal mol-1, respectively. 

This type of coordination is useful for highly stereoselective syntheses of cyclopropane derivatives. Reaction of A -cyclohexenyl methyl ether with the Simmons-Smith reagent gives CM-2-bicyclo[4.1.0]heptyl methyl ether without the trans isomer 103). The Simmons-Smith reaction with 7-tCT f-hutoxynorbornadiene gives syn-exo- IV) and syn-endo isomer (V) without the anti isomers 260). 

Generation of a diazonium intermediate (619) from nitrosourea (618) gave products, which are derived from intermediate 620 (equation 161). Surprisingly, in this special case the C(l)-C(2)-bond of the cyclopropane was cleaved. In contrast, diazonium species of a 3-oxa-bicyclo[4.1.0]heptyl or 3,5-dioxabicyclo[5.1.0]octyl system decomposed via an... 

A general mechanistic problem exists with alkylcarbenes because they are often difficult to detect as metastable intermediates due to intramolecular insertion. In the case of l-(bicyclo[2.2.1]-heptyl)diazomethane (1-norbornyldiazomethane), Bian and Jones (1993) showed that the formation of the carbene can be demonstrated by the stereospecific addition to alkenes, leading to the corresponding cyclopropane derivatives. The stereospecificity is, of course, evidence for trapping the singlet. It is not known yet whether this method has general applicability. 

In 1970 the solvolysis of I-methoxy-2-endo-norbomylbrosylate 25 was shown to yield a product with a bicyclo[3,l,l]heptyl skeleton 26 this seems to be the first example of this kind of contraction of the cycle in the solvolysis of norbomyl derivatives. The formation of ketones 27 and 26 from brosylate 25 points to the migration of C and C. 

In this reaction, too, the stability of the alkyl radical being eliminated influences the ease of fragmentation. The order of ease of elimination based on results from the two studies cited above is t-butyl> isopropyl > benzyl > ethyl >chloromethyl> methyl l-bicyclo[2.2.1]heptyl. Radicals derived from ethers and acetate are also subject to fragmentation, with elimination of a ketone or ester ... 

When the ether oxygen is substituted for C-6 of a bicyclo[2.2.1]heptyl ester, a dramatically different result is observed. Thus the solvolysis of exo-p-bromobenzenesulfonate (124) in buffered acetic acid offers an extraordinary demonstration of anchimeric assistance. While the endo isomer (125) undergoes solvolysis at the rate predicted by the Foote-Schleyer method, the exo isomer (124) reacts some 7 x 10 times faster. This suggests that the ring oxygen is unusually capable of interacting with the back-side lobe of the sp orbital of the exo substituent. R2O-3 participation after ionization was suggested for the endo isomer from product analysis of solvolysis of the deuterated derivative (126). The endo derivative produced 85 %... 

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