Aza‐oxyallyl cations, as proposed by Sheehan in the 1960s have garnered significant attention among the synthetic organic community, owing to their diverse reactivity profile for constructing N‐scaffolds of biological interest. During its initial growth, aza‐oxyallyl cations were used effectively as a 3‐unit synthon as 1,3 dipoles to create N‐heterocycles via cycloaddition reactions, wherein aza‐oxyallyl cation served as electrophilic counterpart. Recently, new variations of aza‐oxyallyl cations reactivity have been reported, including its usage as a 1,4 dipole in cycloaddition reactions, domino reactions, and the unique alkylating ability of heteroatoms. This review article provides an update of the recent developments in this area and the prevailing mechanistic insight.
The Cover Feature illustrates the generation of diverse N‐heterocyclic scaffolds and N‐architectures generated via 3+m cycloaddition reactions or alkylation of a common aza‐oxyallyl cation intermediate in analogy to a flower where various petals originate from the same centre. Cover picture created by Ms. Deeksha and Dr. Ritesh Singh. More information can be found in the Review by Deeksha and R. Singh.
Herein,
we report a highly efficient and unprecedented
approach
for heteroarylation of congested α-bromoamides via electrophilic
aromatic substitution of imidazo-heteroarenes and indolizines under
mild reaction conditions (room temperature, metal, and oxidant free).
The participation of an in situ generated aza-oxyallyl cation as an
alkylating agent is the hallmark of this transformation. The method
was readily adapted to synthesize novel imidazo-heteroarene-fused
dibenzoazepinone architectures of potential medicinal value.
Herein, we report a new and highly efficient approach
for synthesizing
congested α-thioamides under mild reaction conditions (mild
base, room temperature, and short duration) using α-halo hydroxamates
as direct alkylating agents. The reaction works well with both (hetero)aryl
and alkyl thiols, tolerating a broad functional group and diverse
substrate scope, including benzeneselenol for selenoether construction.
The strategy enables efficient synthesis of biologically relevant
1,4 benzothiazinone and 4,1-benzothiazepinone cores, along with various
other functionalized sulfur-based scaffolds of biological importance.
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