Gold-catalyzed formal [4π + 2π]-cycloadditions of propiolate derivatives with unactivated nitriles

Abstract

Gold-catalyzed hetero-[4π + 2π]-cycloadditions of tert-butyl propiolates with unactivated nitriles are described. This new finding enables a one-pot gold-catalyzed synthesis of highly substituted pyridines.

Lactonization of C(sp2)—H Bonds in Enamides with CO2

“…The following neutralization and cyclization generate the desired product 2 in the presence of acid and anhydride. [12] Scheme 5 Possible mechanism…”

“…Synthesis of 4. [12] 2a (0.2 mmol, 49.8 mg) and diethyl but-2ynedioate (0.8 mmol, 136 mg) were added to 2 mL o-xylene under N 2 and the reaction mixture was allowed to stir at 150 °C for 24 h. Then the reaction mixture was cooled to room temperature and evaporated to afford a residue. Separation of the residue by silica gel column chromatography (eluents: PE/EA, V : V＝10 : 1) provided the desired product 4 (0.18 mmol, 67.5 mg, 90% yield).…”

“…2,4-Diphenyl-6H-1,3-oxazin-6-one (2a). [12] 9,160.1,142.7,133.3,131.7,130.1,129.7,128.8,128.8,127.4,100.9,21.6;HRMS (ESI) 4-(4-Methoxyphenyl)-2-phenyl-6H-1,3-oxazin-6-one (2c). [12] 47 mg, 0.…”

“…[12] 9,160.1,142.7,133.3,131.7,130.1,129.7,128.8,128.8,127.4,100.9,21.6;HRMS (ESI) 4-(4-Methoxyphenyl)-2-phenyl-6H-1,3-oxazin-6-one (2c). [12] 47 mg, 0. 9, 162.8, 161.4, 160.2, 133.3, 130.2, 129.3, 128.8, 128.7, 126.8, 114.4, 99.6, 55.5…”

“…2, 159.7, 159.4, 134.2, 134.2, 133.6, 132.8, 131.9, 128.9, 128.6, 127.3, 100.8 4-Cyclohexyl-2-phenyl-6H-1,3-oxazin-6-one (2u). [12] 6, 162.9, 159.9, 133.1, 130.0, 128.7, 128.5, 103.4, 45.0, 30.6, 25.9, 25.8 6H-1,3-oxazin-6-one (2v). [12] 38 mg, 0.176 mmol, 88% yield.…”