Schreiner's Thiourea Promoted [2+2] Cycloaddition of Captodative Azetidinones and Nitroolefins

Abstract

Strained, captodative benzylideneazetidinones were demonstrated to function as potent reaction partners in thermal [2+2] cycloadditions with nitro alkenes. The relief of strain during the cycloaddition could be leveraged to secure kinetic and thermodynamic stability for the aminonitrocyclobutane ring. Accordingly, this mild and robust procedure could be used to simplify the synthesis of azaspiro[3.3]heptanes, a motif that serves as a rigid piperidine bioisostere.

Strain and Complexity, Passerini and Ugi Reactions of Four‐Membered Heterocycles and Further Elaboration of TOSMIC Product

“…However, we found that under identical conditions, only the competing Passerini product was formed. We assumed that the required imine intermediate formation was hampered and the process halted at the hemiaminal stage due to the ring strain [51,52] . To facilitate the imine formation from the hemiaminal and activate the imine intermediate, [53] we probed various polar and protic solvents.…”

A computational study into the origin of reactivity and selectivity of organocatalyzed [2 + 2] reactions between α,β‐unsaturated aldehydes and nitroolefins

“…To study the performance of organocatalysts and Hbonding effects on the reaction, we investigated the reactions between 1a and 2a catalyzed by 3b, 3c, 3d, and 3e (denoted as reactions [11][12][13][14], respectively. Catalyst 3b was obtained by phenyl replacing 3,5-(CF 3 ) 2 -Ph of 3a.…”

“…In recent years, organocatalytic [2 + 2] cycloadditions have received widespread attentions since they are low cost and environmentally friendly . In particular, organic amines employed as catalysts for [2 + 2] cycloadditions have led to a rising interest.…”

NMR and Computational Studies on the Reactions of Enamines with Nitroalkenes That May Pass through Cyclobutanes

“…Despite the fact that formation of cyclobutane derivatives from enamines and electron-withdrawing group (EWG)-substituted alkenes has been reported since the 1960s (for representative instances see Figure 1), 2 most papers seldom mention the role or involvement of cyclobutanes as intermediates. The more recent works of the groups of Seebach, Hayashi, Blackmond, Pihko, and Papai are the exception.…”