Lithium 2,5-dimethylpyrrolate, reaction with

Reaction of lithium 2,5-dimethylpyrrolate ion with [RhCl(CO)2]2 leads to formation of 84 (88PAC1193 90P1503). This is the first example of the mixed mode, when the ti N) and ti (C=C) coordination are realized simultaneously. Nucleophilic addition of triphenylphosphine and triphenylarsine gives 85 (E = P, As). The iridium analogs of 84 and 85 have also been synthesized. 

Reactions of Pyrroles. Pyrroles are efficiently alkylated at the nitrogen atom by alkyl halides in the presence of potassium hydroxide and 18-crown-6. In a study of the metallation of a series of A7-alkyl-pyrroles by butyl-lithium it was found that the ratio of 2,4- to 2,5-dilithio-compounds increases with increasing bulk of the alkyl group.Nitration of 1-methylpyrrole yields a mixture of 2,3-, 2,4-, 2,5-, and 3,4-dinitro-compounds, while 1,2-dimethylpyrrole gives the three possible mononitro- as well as 3,4-, 3,5-, and 4,5-dinitro-derivatives. ° ... 

Methylpyrroles have been converted into pyridines by hydrochloric acid under severe conditions, and also by pyrolysis (p. 109). The formation of a 3-chloropyridine derivative from a pyrrole under Reimer-Tiemann conditions has been mentioned (p. 63). This type of reaction was discovered by Ciamician and Dennstedt treated pyrrole with chloroform in ether and isolated a small yield of 3-chloropyridine. Subsequently, similar reactions were realized with bromoform, carbon tetrachloride, methylene iodide and benzal chloride. Those of several of these reagents with lithium pyrrole in ether and sodium pyrrole under various conditions have been compared. The yields of pyridine derivatives were always low. In submitting 2,5-dimethylpyrrole to the Reimer-Tiemann reaction, Plancher and Ponti23 isolated a pyrrolenine (7). This and its analogues are not intermediates in the conversion of pyrroles into 3-chloropyridines. The idea that dichlorocarbene is the active reagent in reactions using chloroform is supported by recent work 22 ... 

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