Blue Light-Emitting Diode-Mediated In Situ Generation of Pyridinium and Isoquinolinium Ylides from Aryl Diazoesters: Their Application in the Synthesis of Diverse Dihydroindolizine

Abstract

Blue light-emitting diode-mediated environmentally sustainable three component reactions among pyridine/ isoquinoline 1/2, aryl diazoesters 3, and acrylic ester/3-alkenyl oxindoles 5/6 provide various dihydroindolizines 7 to 9 in excellent yield. The principle of the strategy is photolytic generation of nitrogen ylides from N-heteroarenes and aryl diazoesters and their subsequent [3 + 2] cycloaddition reaction with dipolarophiles. Detailed mechanistic analysis of the transformation through control experiments establishes this strategy as the foundation for the photolytic multicomponent reaction.

Visible light-mediated photolysis of organic molecules: the case study of diazo compounds

“…47 Cyclopropenations could be also performed with terminal alkynes 48 and sterically hindered propargyl alcohols; 49 while a number of formal cycloadditions has been also successfully achieved, such as [4+1], 50 [5+1] 51 and [2+2+1]. 52 N-H insertions were reported with amines, 15,43 indoles, 43,53 carbazoles, 43,54,55 pyrazoles, 55 1,2,3-triazoles, 55 amides, 56 sulfonamides, 56 imides, 56 and isatines. 56 O-H insertions were also successfully accomplished with carboxylic acids, 15 perfluorinated alcohols, 57,58 alcohols, 15,59 phenols, 60 oximes, [61][62][63] hydroxamic acids (generated in situ from a NHC catalyst, aldehydes and nitroso compounds) 64 and phosphinic acids (generated in situ presumably from the air oxidation of H-phosphine oxides).…”

Visible‐Light‐Mediated Direct Expeditious Photochemical Construction of Spirocyclic‐Oxindoles

“…Initially, the light-mediated Knoevenagel condensation of malononitrile 9 and isatin 8 a occurs through Int-2, to provide Int-3. On the other hand, the photoexcited state Na In 2021, Sen and co-workers [92] discovered a metal-free visible-light promoted three-component reaction of 3-alkenyl oxindoles 20, aryl diazo esters 21, and pyridine 22 to deliver the spirocyclic-dihydroindolizine-oxindoles 23 in moderate to good yields (63-81%) (Scheme 9). The reaction with 3-alkenyl oxindoles possessing N-Acetyl (R 1 = Ac) substitution provides the desired products as a mixture of diastereomers with a 3 : 1 to 6 : 1 diastereomeric ratio.…”

A Combination of Computational and Experimental Studies to Correlate Electronic Structure and Reactivity of Donor–Acceptor Singlet Carbenes

“…[27][28][29][30][31][32][33] In the recent past, blue LED induced metal-free D-A carbenes have emerged as a promising tool towards the development of various synthetic transformations. [34][35][36][37][38][39][40][41][42][43] However, one of the limitations of D-A singlet-carbene research is that these species are not stable enough to generate crystal structure. Consequently, theoretical prediction and experimental evidence complemented each other to elucidate mechanistic possibilities in most of the cases.…”

“…Reactivity of D-A carbene with the nucleophiles has been investigated in a number of reports. 36,37,[39][40][41] Most of them indicated that the lone pair at the nucleophiles (such as O or N etc.) attack the empty p-orbital of carbene generating O/N-H inserted products in a concerted manner.…”