Mild bromination of unreactive aromatic compounds

Halogenation of aromatic compounds with N-halosuccinimides (NXS) catalysed by D-camphorsulfonic acid-BiCl3

Aromatic bromination catalysed by 0.5-10 mol% of D-camphorsulfonic acid-BiCl3 with N-bromosuccinimides (NBS) was carried out in MeCN under air conditions, and the procedure was extended to the reactions with N-chlorosuccinimides (NCS) and N-iodosuccinimides (NIS). The halogenation of some drugs and natural products was also attempted. One-pot bromination/Suzuki-Miyaura cross-coupling and bromination/Sonogashira coupling reactions were achieved without the removal of the solvent.

Predictable site-selective functionalization: Promoter group assisted para-halogenation of N-substituted heteroaromatics under metal-free condition

Herein, regioselective para-C-H halogenation of N-pyrimidyl (hetero)aromatics through S_EAr (electrophilic aromatic substitution) type reaction is disclosed. S_EAr type reaction has been utilized for the C5-bromination of indolines (para-selective) with N-bromosuccinimide under metal and additive-free conditions in good to excellent yields. The developed methodology is also applicable for iodination and challenging chlorination. The pyrimidyl group is identified as a reactivity tuner that also controls the regioselectivity. The present method is also applicable for selective halogenation of aniline, pyridine, indole, oxindole, pyrazole, tetrahydroquinoline, isoquinoline, and carbazole. DFT studies such as Fukui nucleophilicity and natural charge maps also support the observed p-selectivity. Post-functionalization of the title compound into the corresponding arylated, olefinated, and dihalogenated products is achieved in a one-pot, two-step fashion. Late-stage C-H bromination was also executed on drug/natural molecules (harmine, etoricoxib, clonidine, and chlorzoxazone) to demonstrate the applicability of the developed protocol.

Synthesis of 3-oxadiazole-substituted imidazo[1,2-a]pyridines by nickel immobilized on multifunctional amphiphilic porous polysulfonamide–melamine

A novel efficient and environmentally friendly approach for the synthesis of 3-oxadiazole-substituted imidazo[1,2-a]pyridines in the presence of nickel immobilized on amphiphilic polysulfonamide–melamine is described.

Dual C-F, C-H Functionalization via Photocatalysis: Access to Multifluorinated Biaryls

Multifluorinated biaryls are challenging to synthesize and yet are an important class of molecules. Because of the difficulty associated with selective fluorination, this class of molecules represent a formidable synthetic challenge. An alternative approach to selective fluorination of biaryls is to couple an arene that already possesses C-F bonds in the desired location. This strategy has been regularly utilized and relies heavily on traditional cross-coupling strategies that employ organometallics and halides (or pseudohalides) in order to achieve the coupling. Herein we report conditions for the photocatalytic coupling via direct functionalization of the C-F bond of a perfluoroarene and C-H bond of the other arene to provide an expedient route to multifluorinated biaryls. The mild conditions and good functional group tolerance enable a broad scope, including access to the anti-Minisci product of basic heterocycles. Finally, we demonstrate the value of the C-F functionalization approach by utilizing the high fluorine content to systematically build complex biaryls containing between two and five Caryl-F bonds via the synergistic use of photocatalysis and SNAr chemistry.

Solvent-free synthesis of triazines using N-halosulfonamides

We have developed an efficient procedure for the synthesis of 1,2,4-triazine derivatives using [TBBDA] and [PBBS] as new catalysts.

Poly(N-bromo-N-ethyl-benzene-1,3-disulfonamide) and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide as new efficient reagents for one-pot synthesis of furano and pyrano pyrimidinones (thiones)

We have developed an efficient procedure for the synthesis of furano and pyrano pyrimidinones (thiones) using PBBS and TBBDA as new reagents.