[4 + 2]-Cycloadditions of 3-amino-4-imino-4H-thieno[3,4-c][1]benzopyran with some selected dienophiles

Studies with condensed amino‐thiophenes: Further investigation of reactivity of amino‐thieno‐coumarines and amino‐thieno‐benzo[h]coumarines toward electron‐poor olefins and acetylenes

“…In the light of this last finding and in the light of well-accepted thermal instability of thiepins [5], we have decided to look further into the structure of thiepins claimed to be formed in the previous work [6] as a part of continued investigation on reactivity of condensed thiophenes toward olefins and acetylenes.…”

“…Some times ago Döpp et al [5] have proposed the formation of thiepin 3a (R 1 = CO 2 Me) from reaction of 2a with dimethylacetylene dicarboxylate (Scheme 2). Later our group has reported as well the formation of similar thiepins [6] 3b-c by reaction of condensed thiophenes 2b-c with acetylenic esters.…”

Alkyl heteroaromatic as precursors to polycyclic heteroaromatics: Recent developments

“…In the light of well-accepted thermal instability of thiepins 50 and to see whether the rearrangement into thiepins is a general reaction, we decided to look further into the structure of thiepins claimed to be formed in the previous work. 8 Elnagdi et al 48 investigated the reaction of 91a with ethyl propiolate in the cold to yield a 1:1 adduct that had been earlier assumed to be a thiepinochromone 112b.…”

Reactions of some annelated 2-aminothiophenes with two naphthoquinones

“…17,18 We recently reported 19 the preparation of the condensed benzoxepin 4 from the thienocoumarin 2a and 2,3-dichloro-1,4-naphthoquinone (3a) in refluxing THF in the presence of triethylamine, as the so far only successful reaction from several attempts to induce reactions between 2a and numerous quinones. THF reflux…”