Solvent-controlled switchable domino reactions between 2-alkylidenebenzothiophene-3(2H)-ones and Morita–Baylis–Hillamn (MBH) carbonate were developed. All domino reactions exhibited excellent regioselectivity, producing a broad spectrum of benzothiophene-fused α-pyran, 2,3-dihydrooxepine, and oxatricyclodecene derivatives. Furthermore, [4 + 2], [4 + 3], and related domino reactions from identical substrates can be controlled.

AbstractSpirooxindoles bearing a 1-azabicyclo[5.3.0]decane moiety were synthesized in one step via direct functionalization of the azepane without a transition metal or oxidants. This is an efficient process for the synthesis of fused 7/5-heterobicyclic systems in one step. Furthermore, cycloaddition of the in-situ-generated azomethine ylide only proceeded for alkenyl sulfone dipolarophiles.

We first reported an example of diverse synthesis of pyrano[2,3-b]indol and dihydropyrano[2,3-b]indol from the same starting materials. In these domino reactions, we can control the reaction conditions to give three new products: pyrano[2,3-b]indol, dihydropyrano[2,3-b]indol with E or Z exocyclic double bond. Using DABCO as catalyst in THF, dihydropyrano[2,3-b]indol with E exocyclic double bond and pyrano[2,3-b]indol were obtained at room temperature and 65 °C, respectively. In contrast, when DMAP was selected as catalyst, dihydropyrano[2,3-b]indol with Z exocyclic double bond was formed in toluene at 80 °C.