2,2-Dimethyl-1-(7-methyl-6-((trimethylsilyl)ethyny l)-2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazin-1-yl)pr2,2-Dimethyl-1-(7-methyl-6-((trimethylsilyl)ethynyl)-2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazin-1-yl)propan-1-one2,2-Dimethyl-1-(7-methyl-6-((trimethylsilyl)ethynyl)-2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazin-1-yl)propan-1-one