Acylated Ketenimines and Allenes from Oxazol‐5(4H)‐ones and Furan‐2(3H)‐ones

Abstract

ish black a-thioxothioamides (lo), a class of substances of which only one example has hitherto been reported"].The mixture of (3) and (4, which is also readily accessible in larger quantities, is thus a valuable starting material for products which presumably would be formed from the still unknown (21. c101@c102 Fig I . Molecular structure of the trisulfane 14a) in the crystal (ORTEP diagram): vibration ellipsoids with 30% probability. -Space group P2,2,2,. a = 2655.6, b = 1173.5. c=629.1 f O . l pm. Z=4, p= 1.48 g cm '. The intensities of the reflections were measured with an automated single crystal diffractometer Syntex P2, (CuKC. radiation) and corrected in the usual way. The crystal structure was determined on the basis of 1584 symmetric independent structure amplitudes by the direct method using the computer program MULTAN and refined to R=6.8% (R,=6.1%). On heating (distillation) [(3) + (4)] one obtains acyl chlorides (7) and (Sb), but not the pure a-chlorosulfenyl chlorides (3), and under no circumstances (2)lz1. Recent reports of Pizey and SymeonidesI'l, in which only pivaloyl chloride (7a), i. e. the thermolysis product of [(3a) + (4a)], could be obtained on reaction of pinacolone with thionyl chloride, are to ( 9 )

Mechanistic Diversity in Thermal Fragmentation Reactions: A Computational Exploration of CO and CO2 Extrusions from Five-Membered Rings

“…200–250 °C in condensed phases, or above 300 and 500 °C, respectively, on FVT . In a similar way, 4-methyleneoxazolones (azlactones) 7 extrude CO to form N -acylketenimines 8 in good yields on FVT at 600 °C …”

Formation of Allenyl Ketones, 3-Ethynylcoumarins, and Arylfurans, Furylfurans, and Furylthiophenes by Flash Vacuum Thermolysis of 3-Methylidenefuran-2(3H)-ones

“…Examples are the formation of acylketenes, thioacylketenes, and imidoylketenes by FVT of furan-, thiophen-, and pyrrole-2,3-diones (eq 1) and of N -acylketenimines from 4-methylenoxazol-5(4 H )-ones (eq 2). All of these reactions take place with activation energies ranging from ca. 23 to 50 kcal/mol .…”

“…In a similar manner, 3-methylenefuran-2(3 H )-ones 1 undergo extrusion of CO to form 4-arylallenyl ketones 2 upon FVT at ca. 700 °C (eq ) . While these allenes can be isolated at room temperature, they are generally unstable and should be stored below −20 °C.…”