Neuartige Cycloadditionsreaktionen von 2‐ und 4‐Vinylpyridin mit N‐Alkyl‐maleinimiden

Abstract

(13. XI. 72) Sumnnzary. 4-Vjnylpyridine (la) combines with 3 moles of dienophilic N-alkyl-maleinimides (2) in the presence of polyrncrization inhibitors. The first stcp of the reaction probably consists of 1 : 1-addition with participation of an aromatic double bond, compa.rablc to the analogous bchavior of styrene and its derivatives undcr similar conditions. The unstable intermediates 3, like other Schzffbascs (imincs), add 2 further molcs of the N-alkyl-malcinimides forming thc spiro compounds 4. These are split in an acidic medium into the N-allryl-5,6,7,8~tetraliydroisoquinoline-7,8-dicarboximidcs (5). and N, N'-dialkyl-2-butcne-1, 2,3,4-tetracarboxylic 1,2, : 3,4-diimides (6). LiAIH,-reduction of thcse two types of compounds leads to N-alkyl-l11-(3,4-d)-pyrrolo-2, 3,3 a,4,5,9b-hexahydroisoquinolines (7) and t o N, N'-dialkyl-3,3'-L1ipyrrolidyls (8A) and their dehy dro-products 8B, respcctively.From the reaction of 2-vinylpyridine (lb) with N-alkyl-rnaleinimides (2) the 1 : 2-addition products 9 can be isolated in thc presence of polymcrization inhibitors, which are derivatives of N-alkyl-5,6,7,8-tctrnhydrocluinolinc-~, 6-dicarboxirnicles (9). This agsin corrcsponds to the reaction typc of cycloacltiitions with styrcnc. Furthermore 1 : 3 adducts are formed which according to ly have the structure 10, representing a new type of cycloaddition

My journey from organic to bioorganic chemistry

“…The mechanism of the latter reaction probably operates by way of addition products with a zwitterionic structure, according to eqn. (7) (58). k'nQ'J +3B (7) Imidazole also catalyzes the poly condensation of nucleotide analogs (59).…”