Heterocyclics 3-azabicyclo nonanes

Finally, it must be mentioned that phenylselenation of some diolefins may provide a suitable method for the construction of heterocycles containing two phenylseleno groups. For instance, 3 reacts142 with lV-(phenylseleno)phthalimide (NPSP) in the presence of cyanamide (FENCN) to give the regioisomeric 9-azabicyclo[3.3.1]- and 9-azabicyclo [4.2.1]-nonanes, 173 and 174, as the result of a combined process of inter- and intramolecular nucleophilic addition of cyanamide (equation 140). 

Enehydroxylamines (102) are invoked as intermediates in the rearrangement of O-vinyl, acyl or aryl oximes (101) (equation 31). Varlamov and coworkers demonstrated that the heterocyclization of ketoximes (103) with acetylene in snper basic medium and in the presence of metal hydroxides proceeds by a [3,3]-sigmatropic rearrangement of the enehydroxylamine 105 of the corresponding oxime vinyl ethers 104 (equation 32). The unreactivity of 3-methyl-2-azabicyclo[3.3.1]nonan-9-one oxime (106) in the same reaction conditions was explained by its inability to isomerize to the corresponding enehydroxylamine. 

The photochemistry of certain A-substituted heterocycles has also been studied. As part of a continuing investigation of the photolysis of A-nitroso compounds in solution, the conversion of A-nitroso-3-azabicyclo[3.2.2]nonane (65) into the oxime (66) by photolysis in the presence of acid was reported.58 N-Nitrosopyrrolidine is similarly transformed. The mechanism of this reaction is said58 to involve elimination of NOH with the formation of an imine as intermediate, and, in fact, in the photolysis of 2-ethyl-A-nitrosopiperidine (67), the tetrahydropyridine (68) is the major product. This mechanism certainly does not operate in the photolysis of iV-nitroso-2-azacyclo-octanone, which can be rationalized on the basis of an intramolecular hydrogen transfer [Eq. (16)].59 Acyclic iV-nitrosoamides behave in a similar fashion to IV-nitrosoamines.60... 

Until recently, the intramolecular cyclization procedure had been used only to synthesize fused heterocyclic structures. The first report of a bridged product, in 1978, involved only a minor amount (9%) of an azabicyclo[3.3.1]nonane derivative obtained from the reaction of ds-carveol with acetonitrile and BFj-EtiO. However, several effective examples are now known. These all involve reaction of the nitri-lium intermediate with an internal alkenic nucleophile to yield a 1-azacyclohexene ring and a new carbe-nium ion which undergoes conventional, but stereospecific, Ritter reaction fiom the least hindered face. Such reactions are typified by formation of the multicyclic structures (64 equation 38) 5<) and (65 equation 39), 5i considerable potential in the synthesis of complex nitrogen heterocyclic systems... 

Nuclear Magnetic Resonance Spectroscopy.—As noted above, conformational analysis of bicyclo[3.3.1]nonanes is still a topic of considerable interest. A variable-temperature n.m.r. analysis now provides the first case in which the boat-chair-chair-boat equilibrium is directly observed in the amines (17) and (18). In a related case, re-examination of the acetal (19) suggests that the preferred conformation involves a chair carbocyclic ring and a boat heterocyclic ring. This conclusion was made by n.m.r. analysis, using lanthanide shift reagents, by a study of nuclear Overhauser effects, and by measurement of relaxation times of protons. Details have been reported for other 3-azabicyclo[3.3.1]nonanes, and the non-additivity of substituent effects on chemical shifts in 9-thiabicyclo[3.3.1]non-2-enes has been analysed. Both and n.m.r. data have been reported for a series of 9-borabicyclo[3.3.1]non-anes and their pyridine complexes. 

From a structural point of view, the 38 alkaloids so far obtained from the Daphniphyllaceae are classified into six types of nitrogen heterocyclic skeleton represented by daphniphylline (1), secodaphniphylline (2), daphnilactone-A (3), daphnilactone-B (4), yuzurimine (5), and daphnigracine (6), as shown in Fig. 1. Of the alkaloids, the 9 daphnigracine-type alkaloids are distinct from the other types in the following point they have no 2-azabicyclo[3.3. l]nonane ring system in their structure. 

Cumulative Index of Heterocyclic Systems 4-Azabicyclo[5.2.0]nonane (45)... 

Varlamov, A.V., L.G. Voskresensky, T.N. Borisova et al. 1999. Heterocyclization of tro-pinone and 3-methyl-3-azabicyclo[3.3.1]nonan-9-one oximes with acetylene in super-basic medium. Khim Geterocicl 5 683-687. 

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