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

Gold-catalyzed hetero-[4π + 2π]-cycloadditions of -butyl propiolates with unactivated nitriles are described; the resulting 6-1,3-oxazin-6-ones are not easily accessible conventional methods. This new finding enables a one-pot gold-catalyzed synthesis of highly substituted pyridines through sequential gold-catalyzed reactions of -butyl propiolates with nitriles, and then with electron-deficient alkynes in the same solvent. The utility of these [4 + 2]-cycloadditions is further expanded with various aldehydes, ketones and 2-phenyloxetane, yielding satisfactory yields of cycloadducts.

Gold-catalyzed formal [4π+2π]-cycloadditions of tert-butyl propiolates with aldehydes and ketones to form 4H-1,3-dioxine derivatives.

Gold-catalyzed formal hetero-[4π+2π] cycloadditions of tert-butyl propiolates with carbonyl compounds proceeded efficiently to yield 4H-1,3-dioxine derivatives over a wide scope of substrates. With acetone as a promoter, gold-catalyzed cycloadditions of these propiolate derivatives with enol ethers led to the formation of atypical [4+2]-cycloadducts with skeletal rearrangement.