TEA in acetonitrile T=55°C; 6 h;

barium dihydroxide in water 1 h; Heating;

1: 88 percent / Ba(OH)2*8H2O / H2O / 1 h / Heating 2: 1.) LDA, 3.) TsOH / 1.) THF, 0 deg C, 1h, 2.) photooxygenation/ether, -78 deg C, 3.) THF, -78 deg C View Scheme