Inverse Electron-Demand Aza-Diels-Alder Reaction of α,β-Unsaturated Thioesters with In Situ-Generated 1,2-Diaza-1,3-dienes for the Synthesis of 1,3,4-Thiadiazines

A highly regioselective inverse electron demand aza-Diels-Alder reaction of alpha,beta-unsaturated thioesters with 1,2-diaza-1,3-dienes generated in situ from alpha-halogeno hydrazones was developed. With alpha,beta-unsaturated thioesters as C=S dienophiles, the developed protocol enables the formation of diverse 3,6-dihydro-2H-1,3,4-thiadiazine derivatives in excellent yields. In the presence of lithium aluminum hydride, 3,6-dihydro-2H-1,3,4-thiadiazine derivatives could be further transformed into 5,6-dihydro-4H-1,3,4-thiadiazines in good yields.

Automated summary

A highly selective reaction method using inverse electron demand was developed, allowing the formation of diverse compounds in high yields. The reaction involved the interaction between unsaturated thioesters and 1,2,1,3-diazadienes, generated in situ from alpha-halo hydrazones.