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We report here our synthetic approach to acetylenic esters of six different steroids. The use of flash vacuum pyrolysis (FVP) is a very appealing tool for the acetylenic moiety to efficiently cyclize and rearrange which allows access to medicinally and pharmaceutically valuable products. Each substrate was subjected to FVP. The products were analyzed, identified and characterized. Acetylenic esters of aromatic steroids resulted in 2 H -cyclohepta[ b ]furan-2-one, and 2 H -chromen-2-one derivatives, while aliphatic esters afforded unsaturated polycyclic hydrocarbons via elimination of propiolic acid. [Display omitted] • Acetylenic aromatic steroid esters react via carbene insertion reactions. • FVP of steroid esters provides direct access to prepare interesting fused steroid derivatives. • Acetylenic aliphatic steroid esters undergo elimination reaction via six-membered transition state. [ABSTRACT FROM AUTHOR]

Synthesis and flash vacuum pyrolysis (FVP) of acetylenic esters and ethers of paracetamol and aspirin and their analogues were performed. The products were analyzed, identified, and characterized. Acetylenic esters and ethers of paracetamol resulted in benzofuran, and cyclohepta[ b ]pyrrol-2(1 H)-one. Aspirin and its derivatives produced chromenones, xanthones, indenones, chromenes, and other heterocyclic compounds. [Display omitted] • Synthesis and FVP of aspirinderivatives. • Synthesis and FVP of paracetamol derivatives and analogues. • Valuable routes for synthesis of xanthones and chromenones by FVP. [ABSTRACT FROM AUTHOR]

1-aryl-1,2,3-triazole-4-carboxylate esters 1 - 13 , − 4-carboxamides 14–16 , ethyl 1-aryl-5-methyl/phenyl-1,2,3-triazole carboxylates 17–21 , − 4-carboxamides 22–24 , and 1,4,5-triphenyltriazole 25 have been synthesized via click reactions. Flash vacuum pyrolysis (FVP) for each triazole has been investigated. FVP of triazole-4-carboxylates gave mainly 4-hydroxyquinolin-2(1 H)-one and indole derivatives, while FVP of triazole-4-carboxamides gave indole and urea derivatives. In addition, unanticipated novel products were also isolated. All products were identified, analyzed, and fully characterized. • FVP reaction for twenty-five triazole derivatives were performed. • Indoles and quinolones are the major products from FVP of triazoles at 500–650 ºC. • Methyl triazole-4-carboxylates generate two quinolones isomers. • FVP of 5-substituted triazoles provides two positional isomers of indoles. [ABSTRACT FROM AUTHOR]

• Acetylenic esters of β -hydrogen pyrolyse by a retero-ene reaction. • Acetylenic esters of no β -hydrogen pyrolyse via carbene intermediate. Products from flash vacuum pyrolysis of eleven acetylenic esters are reported in this study. The mechanism of their pyrolysis is proposed based on the products isolated. These reveal a combination of two main mechanistic approaches. Esters with β -hydrogens favor a retro-ene reaction via a six-membered transition state, the absence of such β -hydrogen leads to a carbene intermediate followed by insertion and cyclization. [ABSTRACT FROM AUTHOR]