Photoinduced Electron Transfer Promoted Radical Ring Expansion and Cyclization Reactions of α-(ω-Carboxyalkyl) β-Keto Esters

Abstract

Photoinduced electron transfer (PET) promoted decarboxylation of α-(ω-carboxyalkyl) β-keto esters undergoes radical ring expansion and cyclization reactions. This mild and environmentally friendly method can provide one-carbon expanded γ-keto esters and bicyclic alcohols, and the product distribution is strongly dependent on the length of the alkyl chain containing the terminal carboxylate group.

Decarboxylative Allylation of Amino Alkanoic Acids and Esters via Dual Catalysis

“…The radical decarboxylation of various aryl acetic and α-amino acids following photo- and electrochemical oxidation has been studied for many decades. We were interested in beginning our investigation with (aminoaryl)­acetic acids given that the nitrogen lone pair is more prone to oxidation than carboxylates and the resulting radical has been trapped post-decarboxylation. , For example, photoredox catalysis has been utilized for the decarboxylative radical addition of aminoarylacetic acids to electron-deficient alkenes by Nishibayashi and for the arylation of α-amino acid derivatives by MacMillan …”

Transition metal-free decarboxylative alkylation reactions

“…In 2010, Rouden and co-workers investigated the decarboxylative nucleophilic addition of MAHO 30 to imines (31) under metal-free conditions. 11 Et 3 N promoted the Mannich type decarboxylative addition reaction and various β-amino esters (32) were obtained in moderate to high yields (Scheme 10). When 30 and imine 31a were treated with Et 3 N in DMF-d 7 at −20 °C for a few minutes, a mixture of the diastereoisomers anti-33 and syn-33 were detected by 1 H NMR in situ (Scheme 11).…”

Generation of Alkyl Radicals: From the Tyranny of Tin to the Photon Democracy

“…This expansion was caused by the photocatalyzed decarboxylation of α-(ωcarboxyalkyl) β-keto esters, followed by an exo-trig cyclization of the resulting radical onto the carbonyl group that ultimately led to the one-carbon expanded cycloalkanones by βcleavage. 357 Reduction of indoles having an unactivated haloalkane chain is a useful approach to construct a ring. ).…”

“…Six-membered rings have been likewise obtained by ring expansion in cycloalkanone derivatives. This expansion was caused by the photocatalyzed decarboxylation of α-(ω-carboxyalkyl) β-keto esters, followed by an exo-trig cyclization of the resulting radical onto the carbonyl group that ultimately led to the one-carbon expanded cycloalkanones by β-cleavage …”