Access to 4,5-Dinitro-1,3,5,7-octatetraene Systems

Abstract

The reactions between 1,4‐bis(diethylamino)‐2,3‐dinitro‐1,3‐butadiene (2), easily obtainable by ring‐opening of 3,4‐dinitrothiophene with diethylamine, and 2‐substituted vinylmagnesium bromides gave good yields of the 4,5‐dinitro‐1,3,5,7‐octatetraene derivatives 3a–e. With 1‐phenylmagnesium bromide, conversely, only 3,4‐dinitro‐1,4‐diphenyl‐1,3,5‐cyclooctatriene (4f) was obtained. From the unsubstituted dinitrooctatetraene 3a both the octatriene cycloisomer 4a and the valence tautomer of the latter (6a) could be isolated and characterized. The results obtained evidence an unfavourable effect of the two nitro groups on the cycloisomerization process of the octatetraene system.

Nitrobutadienes from ß-nitrothiophenes: valuable building-blocks in the overall ring-opening / ring-closure protocol to homo- or hetero-cycles

“…As already pointed out, the ring-opening of nitrothiophenes produces appealing building-blocks encompassing a number of versatile conjugated functionalities. A systematic exploitation of their synthetic possibilities began about fifteen years ago for the dinitrobutadienes 5 deriving from 3,4-DNT and only some ten years later for mononitrobutadienes deriving from 3-NT and other β-NT's (11). As far as building-blocks from 2-NT (9) are concerned, we are still at a very initial stage, but they seem to be as much promising as the others.…”

“…The synthetic potentialities offered by the ring-opening products 5 of 3,4-DNT have been extensively examined by us since 1990, and an overview of the main results so far obtained within the overall ring-opening / ring-closure protocol of Scheme 5 is depicted in Schemes 6A-6C. The initial step in the syntheses shown is always represented by the practically quantitative replacement of the two diethylamino groups by reaction with an organometallic compound, namely an aryl (Scheme 6A), 10 vinyl (Scheme 6B) 11 or benzyl Grignard reagent (Scheme 6C). 12 In the latter two cases, nitrosubstituted carbocyclic compounds have been eventually obtained, as the result of interesting processes encompassing electrocyclization steps followed or not by…”

Pyrrolidines, Pyrrolines and Pyrroles from 1,4-Diaryl-2,3-dinitro-1,3-butadienes via a 5-endo-trig Cyclization

“…[1] In the present paper we report on the reactions of dinitrobutadienes 1 with some representative primary amines, a process leading to interesting pyrrolidine derivatives amenable to further transformations, e.g., into pyrrolines 3 and pyrroles 4 (Scheme 1). Scheme 1. i) RNH 2 (3.3 mol equiv.…”

ChemInform Abstract: Synthetic Exploitation of the Ring‐Opening of 3,4‐Dinitrothiophene. Part 9. Pyrrolidines, Pyrrolines, and Pyrroles from 1,4‐Diaryl‐2,3‐dinitro‐1,3‐butadienes via a 5‐endo‐trig Cyclization.

“…In the frame of our studies on the synthetic exploitation of the ring-opening reactions of 3,4-dinitrothiophene and in particular of the ensuing 1,4-diaryl-2,3-dinitro-1,3-butadienes 1, we have shown that the two conjugated nitrovinyl moieties of 1 can be properly modified to furnish aliphatic and heterocyclic targets which are normally difficult to synthesise. [1] In the present paper we report on the reactions of dinitrobutadienes 1 with some representative primary amines, a process leading to interesting pyrrolidine derivatives amenable to further transformations, e.g., into pyrrolines 3 and pyrroles 4 (Scheme 1). Scheme 1. i) RNH 2 (3.3 mol equiv.…”