Tert-Butyl Nitrite-initiated C-N Bond Cleavage of 1-Nitromethyl-N-aryltetrahydroisoquinolines: Synthesis of Furoxans with N-NO Skeleton

A series of furoxan derivatives with N-nitroso groups were synthesized in good yields by TBN initiated radical sp³ C-N bond cleavage of 1-nitromethyl-N-aryltetrahydroisoquinolines. This reaction grafts the biologically important furoxan skeleton and N-nitroso group into on molecule, greatly improving the molecular complexity in one step transformation. The mechanistic study shows that this reaction is mediated by the in situ generated α-carbonyl nitrile oxide, which is afforded by TBN promoted C-N bond cleavage.

Synthesis of 1,2,4-Oxadiazolines through Deoxygenative Cyclization of N-Vinyl-α,β-Unsaturated Nitrones with in Situ Generated Nitrile Oxides from Hydroxamoyl Chlorides

A variety of 1,2,4-oxadiazoline derivatives were synthesized in moderate to good yields through a deoxygenative cyclization cascade reaction of N-vinyl-α,β-unsaturated nitrones and hydroxamoyl chlorides. Mechanistic studies revealed that the reaction underwent double additions of nitrile oxides to N-vinyl-α,β-unsaturated nitrones, sequential elimination, and intramolecular cyclization to afford 1,2,4-oxadiazolines. Alternatively, 1,2,5-oxadiazolines were also obtained as major products in i-PrOH solvent through [3 + 3] cycloaddition and selective [3,3]-rearrangement. Moreover, the prepared 1,2,4-oxadiazolines were easily converted to polysubstituted pyrroles under thermal conditions.

Synthesis of bioactive scaffolds catalyzed by agro-waste-based solvent medium

The backbone of synthetic organic chemistry is the formation of carbon–carbon and carbon–heteroatom bonds. Scientists are actively working to develop new methods of bond-forming reactions because it is one of the most useful tools for the development of structurally diverse molecular entities. On the other hand, scientists are constantly discovering chemical processes to make them more sustainable in order to avoid the ever-increasing chemical emission associated with hazards to the environment. Thus, the development of greener catalytic reactions demonstrated a massive uptick in the ability to carry out carbon–carbon and carbon–heteroatom bond-forming reactions under environmentally friendly and simple reaction conditions. Various approaches are demonstrated, namely, solvent-free, microwave irradiation, ionic liquids, ball milling, ultrasound, one-pot, and aqueous-mediated methods under green chemistry protocol. Agro-waste is the postharvest part or agricultural residues derived from various agricultural activities, which has diverse scope and applications. The use of this agro-waste is an eco-friendly and cost-effective process of waste management. Appropriate and optimal utilization of these waste by-products is one of the major challenges in the present days. The recent trend around the globe is to transform waste into wealth concepts to achieve various applications. Agro-waste-derived ashes and extracted medium are successfully studied recently as a heterogeneous- or homogenous-based catalyst in various organic transformations. Agro-waste-derived catalysts are easily available, cost-effective, simple to prepare, nontoxic, easy to handle, biodegradable, and more environmentally benign. This article focuses more on a few instances of agro-waste-based homogeneous and heterogeneous organic synthesis, especially those used in the construction of bioactive molecule synthesis via C–C and C–X bond formation reactions are discussed. The compiled literature in this article is based on keywords used in the search engine on “agro-waste-based catalyst for organic transformations”, and review articles published on this topic, future scope, and summary are discussed.

Generation of azaarene nitrile oxides from methyl azaarenes and t-BuONO enabling the synthesis of furoxans and 1,2,4-oxadiazoles

A high-efficiency strategy for the synthesis of furoxans and 1,2,4-oxadiazoles has been developed, using tert-butyl nitrite (TBN) as the nitrogen source. Azaarene nitrile oxides were generated in situ via methyl azaarenes functionalization.

Radical Cyclization of 1,n-Enynes and 1,n-Dienes for the Synthesis of 2-Pyrrolidone

2-Pyrrolidones have aroused enormous interest as a useful structural moiety in drug discovery; however, not only does their syntheses suffer from low selectivity and yield, but also it requires high catalyst loadings. The radical cyclization of 1,n-enynes and 1,n-dienes has demonstrated to be an attractive method for the synthesis of 2-pyrrolidones due to its mild reaction conditions, fewer steps, higher atom economy, excellent functional group compatibility, and high regioselectivity. Furthermore, radical receptors with unsaturated bonds (i. e. 1,n-enynes and 1,n-dienes) play a crucial role in realizing radical cyclization because of the ability to selectively introduce one or more radical sources. In this review, we discuss representative examples of methods involving the radical cyclization of 1,n-enynes and 1,n-dienes published in the last five years and discuss each prominent reaction design and mechanism, providing favorable tools for the synthesis of valuable 2-pyrrolidone for a variety of applications.