Formation of pyridazino[6,1-c][1,4]oxazin-8(7H)-ones by intramolecular cycloaddition of azoalkenes

Intramolecular dipolar cycloaddition reaction of 5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olates: synthesis of chiral 1H-pyrrolo[1,2-c]thiazole derivatives

“…Prop-2-ynyloxyacetic acid was prepared from the reaction of propargyl alcohol (prop-2-ynol) and chloroacetic acid by a known method. 7 The reaction of this acetylenic acid with thionyl chloride gave the acid chloride 4a which was used to acylate a mixture of the (2R,4R) and (2S,4R) diastereoisomers of methyl 2-phenylthiazolidine-4-carboxylate 8 3 in the presence of potassium carbonate.…”

“…This was prepared from propargyl (prop-2-ynyl) alcohol (9.51 g, 170 mmol) and chloroacetic acid (17.96 g, 190 mmol) by a procedure described in the literature 7…”

“…The absolute configuration was determined by Flack's method. 12 The refined η parameter was η = Ϫ0.11 (7) (η = 0,1 for the C(1) R and S configuration, respectively). Separated refinements for the two enantiomers gave ωR = 0.0694 (R) and ωR = 0.0744 (S).…”

Hydrazones as substrates for cycloaddition reactions

“…134 Intermediate diazadienes 112 are red liquid substances, more stable than the corresponding acyclic derivatives (Scheme 43).…”

“…the double bond of the cyclopentene moiety, compounds 109 cyclize at room temperature yielding fused tricyclic compounds, namely, hexahydrodiazacyclopenta[cd ]indenones 110 with the cis-disposition of the hydrogen atoms (Scheme 42) 134. …”