Compound 2j
trans-Diethyl 4,8-dimesityl-6,6-dimethyl-5,7-dioxo-4,8-diazaspiro[2.5]octane-1,2-dicarboxylate
From: Diamidocarbenes as versatile and reversible [2 + 1] cycloaddition reagents
From: Diamidocarbenes as versatile and reversible [2 + 1] cycloaddition reagents