Facile Access to Saccharin‐Fused 1,4‐Dihydropyridines through [3+3] Annulation Reactions

Abstract

An efficient approach to saccharin-fused 1,4-DHPs has been established by using a [3 + 3] annulation process. The chemical event was enabled by a Et 3 N-catalyzed tandem Michael/aza-Pinner reaction of alkyl cyclic N-sulfonyl ketimines as nucleophiles with α,α-dicyanoolefins. Under mild conditions, the desired products were readily prepared in good to excellent yields and with broad functional group tolerance (up to 95 % yield, 29 examples). Notably, this practical methodology features the synthesis of pentacyclic spirooxindoles bearing a quaternary spiro-stereocenter.[a] Z.

Synthesis of functionalized 1,4-dihydropyridines containing benzosultams catalyzed by lipase

“…13 Mei's group documented triethylamine mediate [3+3] annulation reactions between saccharin-derived alkyl ketimines and α,α-dicyanoolefins (Scheme 1d). 14 However, in spite of these creative achievements, nucleophilic saccharin derivative-involved reactions are still underdeveloped and in great demand in comparison. Moreover, these documented reactions are always catalyzed by organic base in organic solvents, which, to some extent, do not conform to the concept of green chemistry.…”