Nonane fragmentation

In recent years, a number of complexation agents have been developed that incorporate the bicyclo[3.3.1]nonane skeleton. In a series of publications, selective model receptors consisting of two substituted 3-azabicyclo [3.3.1]-nonane fragments interconnected with various aromatic bridges were described (231 -242 and references therein). The X-ray study of one of them (compound 277) revealed a chair-envelope conformation for the bicyclo[3.3.1]nonane fragments (231) a similar conformation was found in the monomeric compound 278 (231) and in the salts of compounds analogous to 277 (237,238). 

The synthesis of optically active crown ethers incorporating a bicyclo[3.3.1]nonane fragment has been reported recently (compound 285) (249). 

Actinophyllic acid (3), an indole alkaloid with novel l-azabicyclo-[4.4.2]dodecane and l-azabicyclo[4.2.1]nonane fragments, was isolated from the tree Alstonia actinophylla, collected on the Cape York Peninsula, Queensland, Australia, in 2005 by Quinn, Carroll and coworkers [23]. As a carboxypeptidase U inhibitor (IC50 = 0.84 pM), actinophyllic acid shows potential application for the treatment of cardiovascular disorders [23]. Much effort has been devoted to this unique molecule, including recent synthetic studies by Wood and coworkers [24], but only Overman et al. has accomplished its synthesis [25],... 

Hydrozirconations of both vinyl and acetylenic boranes by Srebnik et al. led to 1,1-dime-tallo reagents, which offer the benefits as coupling partners of alkyl- and vinylboranes, respectively [59—62], Initial trials were conducted with B-alkenylborabicyclo[3.3.1]nonanes, but these led to unstable dimetallics. Replacement of the 9-BBN fragment with the pina-colborane-derived analogue produced stable dioxaborolanes 61 (Scheme 4.34). 

Fig. 11.4. Electron ionization mass spectrum of nonanal. Unlike the previous example (toluene, Fig. 11.3), this 9-carbon alkyl aldehyde displays extensive fragmentation and a very low abundance molecular ion at mlz 142. The extensive degree of fragmentation exhibited by many compounds under El conditions makes manual interpretation complex and tedious. Consequently, computerized searches of spectral libraries find extensive use in compound identification.

The derivatives of 2-azabicyclo[3.3.1]nonanes (morphane) (41) can also be used to build the framework of alkaloids with the azocino[4,3-l7]indole fragment. 7-(2-Nitrophenyl)-substituted azabicyclononanone 42 obtained from N-benzylpiperidone-4 (seven stages, total yield (10%)) under the conditions of reductive cyclization has been converted into N-benzylhexahydroazocino [4,3-1 ]-indole 43 (Scheme 10 88T2087). 

Other substituents, e. g. amino, have been found to induce fragmentation of the adamantyl nucleus. Quantitative studies of the solvolysis of aminosubstitu-ted adamantyl bromides (Table 16) suggest that fragmentation occurs simultaneously with ionization. The common product from each of the aminobromoada-mantanes in Table 16 is 3-keto-7-methylenebicyclo[3.3.1]nonane (e.g. Eq. (78))... 

Treatment of 9-oxabicyclo[3.3.1]nonan-l-ols 1014 with a combination of lead tetraacetate and copper diacetate affords 3-allenyl tetrahydropyran-2-ones 1015 via an alkoxy radical accelerated ((-fragmentation pathway (Equation 396) <2001TL2047>. 

A laser flash study of the photoreactions of hexan-2-one and 5-methylhexan-2-one has provided evidence for the existence of the triplet 1,4-biradicals produced by the y-hydrogen abstraction typical of Norrish Type II reactivity. The photochemical behaviour of the alkanone, nonan-5-one, in urea inclusion compounds has been studied. In solution, irradiation of nonan-5-one yields hexan-2-one, propylene, and two cyclobutanols. In the clathrate, the fragmentation products were essentially the same but only one cyclobutanol was observed. The cyclization fragmentation ratio was established as 0.67, compared with 0.32 in methanol. The authors suggest that the CIS-cyclobutanol has less stringent rotational requirements and that it is this isomer (43) which is formed in the clathrate. 

There is continued interest in micellar and surface effects, and unusual reaction media such as polymers, de Mayo and his co-workers have reported further examples of the way in which photoreactions can be modified if one reactant is adsorbed on to silica gel. Irradiation of nonan-5-one as a urea clathrate leads to reduced fragmentation and relatively increased and more selective cyclization in comparison with behaviour in methanol (Casal and... 

The excision of the keto bridge present in tricyclo[5.3.1.1 ]dodecan-l 1-one taken from the work of Cha et al. on synthetic studies of taxol deserves special mention. Highly functionalized derivatives of bicyclo]5.3.1]undecane are obtained using the DIB/I2 system (Eq. 11) [38]. The fragmentation of a related derivative of oxabicyclo[3.3.1]nonan-9-one is used by the same authors as a key step in the synthesis of cK-2,8-disubstituted oxocanes (Eq. 12) [39]. 

The data on the synthesis of azabicyclo[3.3.1]nonanes fused with azoles have recently been published [102-104]. The first step of the reaction is the formation of hydride adducts 125 by action of NaBHa (Scheme 61). These adducts undergo the Mannich condensation with formaldehyde and alkyl amines to give 3-R-l,5-dinitroa-zabicyclo[3.3.1]nonanes 126, fused with azole fragments across the C(7)-C(8) bond. 

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