Azides heterocycles from

Ferndndez-Bolanos JG, Lopez 6 (2007) Synthesis of Heterocycles from Glycosylamines and Glycosyl Azides. 7 31-66... 

D. Lloyd and H. McNab, Angew. Chem., Int. Ed. Engl. 15,459-468 (1976). Synthesis of heterocycles, from vinyl azides ... 

The attempted elimination of five-membered heterocycles from the adducts formal from phenyl azide or diazomethane and hexakis(trifluoromethyl)benzvalene was unsuccessful. The photolysis of the ozonide of the benzvalene at room temperature gives the dimer of tetrakis(trifluoromethyl)cyclobutadiene. When the irradiation is carried out in a matrix at —196 °C, the reaction mixture was coloured yellow. The... 

Kim developed a new entry into A -heterocycles by radical cyclizations onto alkyl azides. Iodides, bromides and thionocarbonates (Scheme 28, Eq. 28.1) are suitable radical precursors. 5-Exo cyclizations afford 3,3-triazenyl radicals that lose N2 to furnish an aminyl radical [79]. Following this work, Kilburn has applied this strategy to the formation of spiro-heterocycles from methylenecyclopropanes [80]. Finally, this reaction was applied as a key step in a very elegant cascade synthesis of aspi-dospermidine developed by Murphy (Scheme 28, Eq. 28.2) [81]. 

Synthesis of Heterocycles from Glycosylamines and Glycosyl Azides... 

SCHEME 18. N-Heterocycles from methyl isoricinoleate produced via the azide, (i) MsCI, NEt3 (ii) NaNg, A/,A/-dimethylformamide (DMF), 50°C (iii) 80°C (iv) NaBH4, MeOH. 

N-Condensed heterocyclics from azides with ring expansion... 

It is well known that alkyl azides also behave as 1,3-dipoles in intramolecular thermal cycloaddition reactions. The formation of two carbon-nitrogen bonds leads to triazolines, which are usually not stable. They decompose after the loss of nitrogen to aziridines, diazo compounds, and heterocyclic imines. There are a limited number of examples reported in which the triazoline was isolated [15]. The dipolar cycloaddition methodology has been extremely useful for the synthesis of many natural products with interesting biological activities [16], In recent years, the cycloaddition approach has allowed many successful syntheses of complex molecules which would be difficult to obtain by different routes. For instance, Cha and co-workers developed a general approach to functionalized indolizidine and pyrrolizidine alkaloids such as (-i-)-crotanecine [17] and (-)-slaframine [18]. The key step of the enantioselective synthesis of (-)-swainsonine (41), starting from 36, involves the construction of the bicyclic imine 38 by an intramolecular 1,3-dipolar cycloaddition of an azide derived from tosylate 36, as shown in Scheme 6 [ 19). 

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