Compound 4b
4,8-Dimesityl-6,6-dimethyl-2-(4-nitrophenyl)-1-oxa-4,8-diazaspiro[2.5]octane-5,7-dione
From: Diamidocarbenes as versatile and reversible [2 + 1] cycloaddition reagents
From: Diamidocarbenes as versatile and reversible [2 + 1] cycloaddition reagents