Chemical Equivalent of Arene Monooxygenases: Dearomative Synthesis of Arene Oxides and Oxepines.

Direct epoxidation of aromatic nuclei by cytochrome P450 monooxygenases is one of the major metabolic pathways of arenes in eukaryotes. The resulting arene oxides serve as versatile precursors to phenols, oxepines, or trans-dihydrodiol-based metabolites. Although such compounds have an important biological and chemical relevance, the lack of methods for their production has hampered access to their utility. Herein, we report a general arenophile-based strategy for the dearomative synthesis of arene oxides. The mildness of this method permits access to sensitive monocyclic arene oxides without any noticeable decomposition to phenols. Moreover, this method enables direct conversion of polycyclic arenes and heteroarenes into the corresponding oxepines. Finally, these studies provided direct connection between simple aromatic precursors and complex small organic molecules via arene oxides and oxepines.

Palladium-Catalyzed Dearomative syn-1,4-Diamination.

Herein we report a dearomative syn-1,4-diamination protocol using simple nonactivated arenes and amines. This one-pot method utilizes arene-arenophile para-cycloadducts, formed via visible-light-mediated [4+2]-photocycloaddition that undergoes formal allylic substitution with amine nucleophiles under Pd-catalysis. The products are obtained with exclusive syn-1,4-selectivity; the method permits enantioselective desymmetrization of naphthalene, as well as elaborations of amine-containing drug molecules. Furthermore, the resulting unsaturated products are amenable to numerous options for diversification. Overall, this novel dearomative functionalization strategy offers rapid and straightforward access to complex building blocks, which are difficult to prepare otherwise, from simple arenes.

Recent advances in chemical dearomatization of nonactivated arenes.

Dearomatization reactions provide a synthetic connection between readily available, simple aromatic starting materials and more saturated intermediates of greater molecular complexity and synthetic utility. The last decade has witnessed a steady increase in the development of dearomative methods, providing new synthetic approaches to high-value building blocks and natural products. This review highlights advances both in the area of dearomatization methodologies for the most chemically inert arenes and in synthetic applications of such strategies.

Nickel-Catalyzed Synthesis of Quinazolinediones.

A nickel(0)-catalyzed method for the synthesis of quinazolinediones from isatoic anhydrides and isocyanates is described. High-throughput ligand screening revealed that XANTPHOS was the optimal ligand for this transformation. Subsequent optimization studies, supported by kinetic analysis, significantly expanded the reaction scope. The reaction exhibits a case of substrate inhibition kinetics with respect to the isocyanate. Preliminary results on an asymmetric synthesis of atropisomeric quinazolinediones are reported.

Nickel-catalyzed decarboxylative cross-coupling of perfluorobenzoates with aryl halides and sulfonates.

A Ni-catalyzed method for the coupling of perfluorobenzoates with aryl halides and pseudohalides is described. Aryl iodides, bromides, chlorides, triflates, and tosylates participate in these transformations to afford the products in good yields. Penta-, tetra-, and trifluorinated biaryl compounds are obtained using these newly developed Ni-catalyzed decarboxylative cross-coupling reactions.

Nickel-Mediated Synthesis of Isoindolinones at Room Temperature.

This communication describes a method for the Ni(cod) 2-mediated intramolecular arylation of alkyl C-H bonds adjacent to the nitrogen atom in benzamide substrates. The transformation proceeds at room temperature and exhibits selectivity for functionalization of more substituted C-H bonds. The yields of the desired isoindolinone products are higher with benzamide substrates containing tertiary alkyl groups on the nitrogen atom than with those bearing primary or secondary alkyls. The results described herein suggest a mechanism involving radical intermediates for these reactions.

Nickel or phenanthroline mediated intramolecular arylation of sp3 C-H bonds using aryl halides.

The development of the intramolecular arylation of sp(3) C-H bonds adjacent to nitrogen using aryl halides is described. Arylation was accomplished using either Ni(COD)2 or 1,10-phenanthroline in substoichiometric amounts, and the reaction conditions were applied to a variety of electronically differentiated benzamide substrates. Preliminary studies suggest a mechanism involving aryl and alkyl radical intermediates.