Intramolecular azavinyl carbene-triggered rearrangement of furans

Abstract

Rhodium-catalyzed decomposition of furyl-tethered 1-sulfonyl-1,2,3-triazoles was demonstrated to have high synthetic potential for the synthesis of densely substituted heterocyclic frameworks.

Heteroarene‐tethered Functionalized Alkyne Metamorphosis

“…This strategy enables as traightforward protocol for the synthesis of 2-acetyl-a nd 2-formylpyridines 422 from biomass-derived furan derivatives (Scheme 107). [128] Au-catalysis was also employed for the intramoleculare lectrophilica romatic substitution (S E Ar) reactiono fi soxazole-tethered propargylamines and ethers 423.U se of 5mol %A uc atalyst alongside 5mol %A gSbF 6 yieldedt he desired cyclized products.I nt he transformation of propargylamines,abetter yield was achieved by use of N-phenylbenzaldimine as an additive for hydride acceptora ccelerating the last stage oxidation step. For propargyl ethers, both terminala nd internal alkynes were found to efficient for this transformation but propargylamine derivative terminal alkyne failed to produce the desired product.…”

“…This strategy enables a straightforward protocol for the synthesis of 2‐acetyl‐ and 2‐formylpyridines 422 from biomass‐derived furan derivatives (Scheme 107). [128] …”

Transformation of 3-(Furan-2-yl)-1,3-di(het)arylpropan-1-ones to Prop-2-en-1-ones via Oxidative Furan Dearomatization/2-Ene-1,4,7-triones Cyclization

“…Based on our experience on the use of furans dearomatization in the synthesis of various heterocycles [ 26 , 27 , 28 , 29 , 30 , 31 ], we assumed that the removal of EWG may lead to a switch of reactivity pattern via the crucial decrease of the enol A ′ form contribution. As a result, the oxidation of oxoalkyl furans, which lack α-EWG-functionality, may lead to different products.…”

Straightforward Access to 2-Iodoindolizines via Iodine-Mediated Cyclization of 2-Pyridylallenes

“…Originally synthesized by Scholtz and Tschitschibabin at the beginning of the 20th century through condensation reactions, new methods, essentially dipolar cycloaddition and cycloisomerization reactions, have been developed since then, giving access to a plethora of polysubstituted indolizine rings as well as indolizines bearing a halogen at position 2 . Although there is growing interest in accessing 1,2,3-trisubstituted indolizines, to the best of our knowledge only Kim and colleagues have proposed a method to synthesize 1,3-disubstituted 2-iodoindolizines from propargylic acetates. , The iodine substituent at the 2-position should allow postfunctionalization through commonly used transition-metal-catalyzed cross-coupling reactions or a radical pathway. Also, a brief literature survey shows that pyridylallenes are valuable intermediates for the synthesis of indolizines via 5-endo-trig cyclization reaction under electrophilic activation. , …”