α,β-Unsaturated Fischer Carbene Complexes vs. 1,3-Dipoles: Reactions with Nitrones and Nitrilimines

Abstract

The reaction of tert‐butylalkynyl chromium Fischer carbene complex 1 with nitrones 2 affords β‐enamino‐ketoaldehydes 4 by the light‐promoted rearrangement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carbene complexes 19 with nitrilimines 10 yields enantiomerically pure Δ2‐pyrazolines with high regio‐ and diastereoselectivity.

Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo‐heterocycles

“…These results were surprising, especially given that we unambiguously established that 3a undergoes a (3+2) cycloaddition when reacted with dimethylacetylene dicarboxylate (K 2 CO 3 , THF, rt, 4 h, 65%),[15a] an organic analogue of Fischer complexes 1 , affording indolizine 4b (Figure )[15b] as the major product (Scheme ). Moreover, this kind of cycloaddition has been reported in the reaction of alkenyl carbenes with 1,3‐dipoles such as nitrilimines, where Δ 2 ‐pyrazolines were formed …”

“…Moreover, this kind of cycloaddition has been reported in the reaction of alkenyl carbenes with 1,3-dipoles such as nitrilimines, where Δ 2 -pyrazolines were formed. [16] It should be stated at this point that there is a clear difference in the reactivity of pyridinium salts with these groups of compounds (alkynyl ester vs alkynyl carbene), despite their structural similarities. For this reason, our investigations turned toward understanding the potential of the unexpected products 5 and 6.…”

Synthesis, characterization, and evaluation of a novel inhibitor of WNT/β-catenin signaling pathway

“…The 1,3-dipolar cycloaddition reaction using nitrilimines is a well-known process [ 22 - 28 ]. This synthesis usually generates the corresponding pyrazolines as a mixture of regioisomers [ 29 - 31 ], but no direct evidence is available to reveal which regioisomers are obtained in this reaction.…”

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

“…Table 25 Photo-driven reaction of Group 6 imine carbenes with alkenes Table 26 Photo-driven reactions of Group 6 imine carbenes with alkynes (38) 1,3-Dipolar cycloadditions to alkynylcarbenes followed by photolysis led to b-enamino ketoaldehydes (Eq. 39) [134]. Photolysis of N-acylamino carbene complexes produced munchnones, which were trapped with alkynes to give pyrroles (Table 27) [135].…”