Pyrrole 2-amino-3-cyano- from

A more complex reaction is involved in the cooligomerization of acetylenes and tert-butyl isocyanide using nickel acetate as the catalyst (Scheme 20)43 the nature of intermediate complexes leading to the formation of 2-cyano-5-terf-butylaminopyrroles has not been established. Cocyclization of tert-butyl isocyanide with coordinated hexafluoro-2-butyne gives rise to coordinated cyclopentadienone anils for molybdenum systems,44 hence the nature of acetylene substitutents and of the organometallic catalyst play crucial roles in these processes. The pyrrole products from the former reaction can be decomposed by sulfuric acid and the overall sequence provides a simple synthesis of 5-amino-2-cyanopyrroles (Scheme 20). 

Formation of the pyridazine ring occurs in a straightforward way from a suitably substituted pyrrole. Thus the pyrrole nucleoside (95) forms the pyrrolo[2,3-rf]pyridazine (96) on treatment with hydrazine <93JMC3834>. Another report describes the preparation of 4-amino-1 -(/i-o-ribo-furanosyl)pyrrolo[2,3-< /]pyridazine (Equation (30)) <91BMClll>. Similar pyrrole nucleosides, with an ester function at position 3 and an aldehyde at position 2, lead to 4-oxo derivatives upon treatment with hydrazine <90JHC1989>, or 4-amino derivatives with a cyano group at position 3 (92JMC526). 

Using the above-mentioned hydrazone intermediates, derived from attack of nucleophilic species bearing carbonyl, cyano or carboxylate functions in a-position, many widely functionalized 1-aminopyrroles have been obtained (i.e. 3-substituted-l-aminopyrroles, l-amino-2,3-dihydropyrrol-2-ols, 1,2-diaminopyrroles, pyrrolo(2,3-6]pyrroles, 1-amino-l//-pyrrol-2(3/J)-ones, and 3-unsubstituted-l-aminopyrroles). The reaction pathway indicates an intramolecular interaction between the >C=N-NH- nitrogen atom and one of the above-mentioned functional groups followed by an appropriate molecular rearrangement and/or elimination, leading to the heterocyclization process. Scheme 1 shows the type of new pyrroles synthesized in our laboratory. 

Toyocamydn 4-amino-5-cyano-7-(D-ribofurano-syl)-pyrrolo-(23-d)-pyrimidine 6-amino-7-cyano-9-P-D-ribofuranosyl-7-deazapurine, a 7-deazaadenine antibiotic from Streptomyces toyocaensis and S. rimosus. M.p. 243 C. Biosynthesis is analogous to that of Tii-bericidin (see), i.e. the carbon atoms of the pyrrole ring are derived from 5-phosphoribosyl 1-pyrophosphate. T. is particularly active against Candida albicans, Saccharomyces cerevisiae and Mycobacterium tuberculosis. 

SCHEME 2.100 Formation of l-amino-3-iminopyrrolizines from 2-(l-ethylthio-2-cyano-vinyl)pyrroles or l-ethylthio-3-iminopyrrolizines and primary amines in water. 

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