Synthesis of methylene cyclopropane-fused chromenes and dihydroquinolines by sequential [4 + 2]- and [1 + 2]-annulation

Abstract

A base promoted sequential [4 + 2]- and [1 + 2]-annulation of 2-hydroxychalcones or 2-tosylaminochalcones with prop-2-ynylsulfonium salts was developed.

Synthesis of CF3, CF2H‐Substituted, Epoxide‐Fused Heterocycles with Prop‐2‐ynylsulfonium salts

“…The yield of 3 aa was optimized by screening a range of bases to maximize the yield (Table 1, entries 1-12). In comparison, the reaction employing other inorganic bases, such as K 2 CO 3 , Cs 2 CO 3 , KOH, t-BuOK, Na 2 CO 3 , KOAc and K 3 PO 4 were unable to generate 3 aa satisfactorily (Table 1, entries 2-3, 8- 12). Interestingly, a significant drop in the yield was observed while using based such as DUB and DMAP (Table 1, entry 4 and entry 7).…”

“…[11] Miao's group reported a [4 + 2]-and [1 + 2]-cyclization reaction of 2hydroxychalcone with prop-2-ynylsulfonium salts forming methylenecyclopropane-concentrated dihydroquinolines (Scheme 1d). [12] In a recent study, Zhu reported the formation of an epoxide fused 2-methylene-pyrrolidone that N-sulfonyl-βamino-1-phenylethanone with prop-2-ynylsulfonium salt (Scheme 1f). [13] Due to our ever-increasing interest in prop-2ynylsulfonium salts and the excellent bioactivity of cyclopropane-fused tetrahydroquinolines, we developed the annulation sequence [4 + 2]/[1 + 2] for fused ring systems with fluorinated and especially CF 3 , CF 2 H-substituted epoxide fused quinolines (Scheme 1).…”

Recent Advances on Annulation Reactions with Allyl and Propargyl Sulfonium Salts

“…They disclosed a sequential [4+2] and [2+1] cyclization of prop-2-ynylsulfonium salts 44 with 2-hydroxychalcones or 2-tosylaminochalcones 53 (Scheme 22, B). 34 By using Cs 2 CO 3 as the base, diverse cyclopropane-fused dihydroquinolines or chromenes 54 were obtained in good yields.…”

Diastereoselective Synthesis of Tetrabenzohydrofuran Spirooxindoles via Diethyl Phosphite-Mediated Coupling of Isatins with o-Quinone Methides

“…Inspired by these studies, and as a continuation of our interest in bioactive fused polycyclic structure synthesis, we here report that o -quinone methides ( o -QMs) act as Michael acceptors in undergoing a domino reaction with isatin derivatives in the presence of diethyl phosphate as an initiator. The method provides efficient access to tetrabenzohydrofuran spirooxindole skeletons that are an important structural motif found in a large number of bioactive compounds.…”