Dimethoxycarben (1) addiert an Fumar- oder Maleinester unter Bildung von 3,3-Dimethoxy-cyclopropan-trans-1,2-dicarbonester (6). Bei der Addition an Styrol-Derivate entstehen ebenfalls 3,3-Dimethoxycyclopropane, wahrend mit Acetylendicarbonester, Phenylacetylen oder Diphenylketen 1:2-Addukte unterschiedlicher Struktur resultieren.



Carbene Reactions, IV. Addition of Dimethoxycarbene to CC Multiple Bonds



Dimethoxycarbene (1) adds to diethyl fumarate or maleate to form diethyl 3,3-dimethoxycyclopropane-trans-1,2-dicarboxylate (6). Addition to styrene derivatives yields similarly 3,3-dimethoxycyclopropanes, whereas addition to acetylenedicarboxylate, phenylacetylene or diphenylketene led to 1:2-adducts of varying structure.

Carben-Reaktionen, IV. Addition von Dimethoxycarben an CC-Mehrfachbindungen

Reactions of o-aminothiophenol withαβ-unsaturated dicarbonyl systems. Facile synthesis of benzothiazines and benzothiazepines

4-Vinylpyridine (1a) combines with 3 moles of dienophilic N-alkyl-maleinimides (2) in the presence of polymerization inhibitors. The first step of the reaction probably consists of 1:1-addition with participation of an aromatic double bond, comparable to the analogous behavior of styrene and its derivatives under similar conditions. The unstable intermediates 3, like other Schiff bases (imines), add 2 further moles of the N-alkyl-maleinimides forming the spiro compounds 4. These are split in an acidic medium into the N-alkyl-5,6,7,8-tetrahydroisoquinoline-7,8-dicarboximides (5), and N,N′-dialkyl-2-butene-1,2,3,4-tetracarboxylic 1,2,:3,4-diimides (6). LiAlH4 reduction of these two types of compounds leads to N-alkyl-1 H-(3,4-d)-pyrrolo-2,3,3a,4,5,9b-hexahydroisoquinolines (7) and to N,N′dialkyl-3,3′-bipyrrolidyls (8A) and their dehydro-products 8B, respectively.



From the reaction of 2-vinylpyridine (1b) with N-alkyl-maleinimides (2) the 1:2-addition products 9 can be isolated in the presence of polymerization inhibitors, which are derivatives of N-alkyl-5,6,7,8-tetrahydroquinoline-5,6-dicarboximides (9). This again corresponds to the reaction type of cycloadditions with styrene. Furthermore 1:3 adducts are formed which according to 1H- and 13C-NMR.-data most likely have the structure 10, representing a new type of cycloaddition involving the pyridine nitrogen.

Th. Wagner-Jauregg

Papers

Neuartige spiroverbindungen durch addition von maleinimiden an schiff-basen

Imidazole als induktoren der cyclo-oligomerisation von n-alkyl-maleinimiden und der cis-trans-umlagerung von maleinsaeure-dimethylester

Neuartige spiroverbindungen durch addition von maleinimiden an schiff-basen