Pyrrolines fused

Reactions of iminyl and related radicals in formation of pyrrolines and fused pyrrolines 96SL1148. 

Japanese researchers varied aryl substituent at C-4 in nitronate (147), LA, and the reaction conditions, they used successfully diastereomerically pure nitronates (147) (Scheme 3.121) for the synthesis of various fused-ring systems, such as benzofuro-[3,2-d]-l,2-oxazines (322), furo-[3,4-d]-isoxazoles (323—326), indolo-[2,3-b]-l-pyrroline 1-oxides (327), 4//-1,2-benzoxazines (328), benzofuro-[2,3-c]-tetrahydropyrans (329), and monocyclic 1,2-oxazines (330). 

Pearson et al. (64) developed an approach to the fused bicyclic 3-pyrrolines 328 based on an intramolecular azide-alkene cycloaddition (Scheme 9.64). Azides (327) were heated at various temperamres between 70 and 110°C to afford the... 

Vinyltriazolines are unique thermolysis leads to high yields of 1-vinylaziridines. This is true of fused-ring tetracyclic (Scheme 40)199,201 and tricyclic triazolines (Schemes 42 and 43)200 204 with vinylic substitution in the 1-position. 1-Vinyltriazoline with no substituents on the ring carbons furnishes 1-vinylaziridine without formation of pyrrolines.378 Thermal decomposition of vinyl azides in acrylic acid derivatives is a synthetic route for 2-substituted 1-vinylaziridines.470 Similarly, aziridine 1-oximes are the only products of thermolysis of triazoline 1-oximes.107... 

Fischer s base (55) reacts with tetracyanoethylene to yield a mixture of spiro and fused pyrrolines, which are believed to arise from an initial zwitterionic adduct, as shown in Scheme 351. 

Metalation of the amine substrate 184, followed by annulation promoted by tetramethylethylenediamine (TMEDA), gave the intermediate 185, which could thereafter be converted to the fused 3-pyrroline system 186 (Scheme 22). Subsequent dehydrogenation with DDQ gave the corresponding fused pyrrole. This methodology was used for preparation of an extended set of related pyrroles, as well as a series of indole derivatives, which were accessed by lithiation of iV-bromoallyl-2-bromoanilines <2001CEJ2896>. 

Heterocycle-fused, 1,5-diazocines have been prepared by nucleophilic attack by nitrogen at the carbon alpha to the hetero atom. Eberle and Houlihan reacted 1,3-propanediamine with the pyrroline 165 and obtained the pyrrolidinodiazocine 166 (71GEP2050344). Wamhoff and Materne treated the dihydrofurans 167 with 1,3-diaminopropane and isolated the... 

Similar cycloaddition reactions of diphenylnitrilimine with pyrrolines and benzopyrroles yield variously substituted fused-ring triazolines 74 and 75 (85AP556). 

Nitrogen Heterocycles. The [3,2-6]-l-pyrroline (231) formed by reductive cyclisation of the nitro-ketone (230) afforded the as-fused [3,2-b]pyrrolidine (232) on partial reduction with NaBH4. With AC2O at room temperature the pyrroline (231) suffered rearrangement to the acid sensitive 0,A -heterocycle (233). 

Hudlicky and Pearson suggested that the formation of the fused pyrrolines (117) by pyrolysis of the azido-dienes (115) would be a useful synthetic procedure if conditions allowing the specific decomposition of the vinylaziridines (116) via cleavage of bond a could be identified. This problem has now been solved simply by incorporating a heteroatom at R1 of the diene unit the acetal-like nature of the intermediate (116) now weakens bond a sufficiently... 

Anthramycin is an antibiotic with antitumor activity. It is isolated from the growth of Streptomyces refuineus. Anthramycin (3.36) is unique in having the 7-membered azepine ring (partially reduced) present, fused to a pyrroline ring (a dihydropyrrole). 

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