AA visible light-mediated, metal-free, regioselective dihydrothionation of terminal aromatic as well as heteroaromatic alkynes has been achieved by using Eosin Y as a photoredox catalyst at room temperature. The protocol...
The
cyanation of organic compounds is an important synthetic transformation
and mainly relies on a toxic CN source. Undeniably, thiocyanate salt
has emerged as a very mild and environmentally benign CN source, yet
its synthetic utility for cyanation is highly limited to very few
types of organic compounds. Herein, we report the direct cyanation
of cyclic thioacetals for accessing compounds with two different functional
groups (thiocyano-thioesters) in one pot using sodium thiocyanate
via photoredox catalysis. The protocol has been further extended for
the direct cyanation of disulfides and diselenide to access aryl thiocyanates
and aryl selenocyanate. A plausible mechanism has been proposed based
on a series of control experiments, cyclic voltammetry and Stern–Volmer
studies.
The rearrangement of dithiolanes and dithianes to access disulfide‐linked‐dithioesters under visible‐light photoredox catalysis via controlled C−S bond cleavage has been disclosed. Unlike, the usual deprotection of dithioacetals to corresponding aldehydes under the oxidative conditions, we observed unique regioselective oxidative reactivity of five and six membered cyclic dithioacetals to form disulfide‐linked‐dithioesters by exchanging DMAP and imidazole bases. The generality of the protocol has been demonstrated by exploring a wide range of substrates. As an application, in situ generated thiyl radical has been trapped with disulfides to prepare hetero‐disulfides of potential utility. The protocol proved to be practical on gram scale quantity and relied on clean energy source for the transformation. Based on the series of control experiments, cyclic voltammetry and Stern‐Volmer studies the plausible mechanism has been proposed.
Quinoxalinones are a privileged class of compounds, and their structural framework is found in many bioactive compounds, natural compounds, and pharmaceuticals. Quinoxalinone is a promising scaffold for different types of functionalization, and the slight modification of the quinoxalinone skeleton is known to offer a wide range of compounds for drug discovery. Owing to the importance of the quinoxalinone scaffold, we have developed a base-mediated protocol for the C3-alkylation of quinoxalinone followed by tandem cyclization to access novel types of strenuous and fused dihalo-aziridino-quinoxalinone heterocycles via the construction of C−C and C−N bonds. The protocol proved to be simple and practical to access desired fused quinoxalinone heterocycles in excellent yields (up to 98% yield). As an application, the highly functionalized fused dihalo-aziridino-quinoxalinone molecule has been further utilized for monodehalogenation under visible light irradiation and selective amide reduction. Moreover, the protocol has also been demonstrated on a gram scale.
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