Synthesis of fully functionalised spiropyran pyrazolone skeletons via a formal [4 + 2] cascade process using β-nitro-styrene-derived MBH-alcohols

Abstract

Cascade synthesis of spiropyrazolone tetrahydropyrans was efficiently carried out under metal free conditions using β-nitrostyrene derived Morita–Baylis–Hillman (MBH) alcohols.

Synthesis of tetrahydrochromenes and dihydronaphthofurans via a cascade process of [3 + 3] and [3 + 2] annulation reactions: mechanistic insight for 6-endo-trig and 5-exo-trig cyclisation

“…20 Previously, our group carried out a [3 + 3] cyclization reaction of β-naphthol with primary MBH acetate to study the scope of S N 2′ vs. S N 2 reaction. 21 With our ongoing interest in using nitro styrene derived MBH adducts 22 explored the reactivity of primary and secondary MBH acetate with β-tetralone 1 as our model reaction. Initially, the reaction carried out using β-tetralone 1 with primary MBH-acetate 2 , predominantly gave a tetrahydrochromene 3 via [3 + 3] annulation involving 6- endo trig cyclization through Michael/oxa-Michael cascade process.…”