General Entry into o‐,o′‐Heteroatom‐Linked N‐(Hetero)aryl‐Imidazole Motifs by Gold‐Catalysed Formal [3+2]‐Dipolar Cycloaddition

Abstract

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Preparation and Utility of N-Alkynyl Azoles in Synthesis

“…The researchers were interested in developing a Co(III)-catalyzed synthesis of amino-substituted isoquinolones via carbon-hydrogen (C-H) activation and were surprised when they isolated 5-aminooxazole as the sole product. Interestingly, the reaction gave the opposite regioisomer compared to previously reported metal-catalyzed syntheses of aminooxazoles [102].…”

“…Reddy reported a copper-mediated addition of 2-aminopyridine to N -alkynyl amides and the N -alkynylindoles 235a – c to afford the indole-substituted imidazolopyridines 236a – c (Scheme 65, Reaction (1) [100]). In 2017, building up their work on gold-catalyzed formal [3 + 2] cycloadditions [101,102], Davies group reported the gold-catalyzed addition of the N , N -dipole 238 to the N -alkynylindole 237 to afford the fused heterocycle 239 (Scheme 65, Reaction (2) [103]).…”

Sulfenyl Ynamides in Gold Catalysis: Synthesis of Oxo‐functionalised 4‐aminoimidazolyl Fused Compounds by Intermolecular Annulation Reactions

“…Aminoimidazole and N ‐fused imidazole motifs have been targeted for methodology development programmes due to their importance as bioactive molecules . Our group introduced a nucleophilic nitrenoid strategy to prepare heteroaromatic‐fused 2‐aminoimidazoles in an expedient and modular fashion by the use of N ‐substituted N ‐pyridinium aminides alongside ynamides . Having established that diazine, pyridine and fused 1,3‐azole substitution patterns can be incorporated, we questioned whether this approach could be used to build imidazole rings around more functionalised and non‐aromatic motifs (Figure a).…”

“…Broad tolerance and applicability was seen when we examined the combination of sulfenyl ynamides with various aminide‐based nitrenoids (Scheme ) . Imidazole‐fused heterocycles 27 – 38 were obtained in generally high to quantitative yields through reactions that were more effective and/or faster than with non‐sulfenyl ynamides.…”

“…[16] Our group introduced a nucleophilic nitrenoid strategy to prepare heteroaromatic-fused 2aminoimidazoles in an expedient and modular fashion by the use of N-substituted N-pyridinium aminides alongside ynamides. [7,17] Having established that diazine, pyridine and fused 1,3-azole substitution patterns can be incorporated, we questioned whether this approach could be used to build imidazole rings around more functionalised and non-aromatic motifs (Figure 2a). Structures featuring imidazole rings fused to oxo-substituted heterocycles have shown potency in medicinal and agrochemical applications (Figure 2b) [18] and hence were deemed appealing targets for the annulation methodology.…”