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We report the non-decarbonylative Mizoroki–Heck reactions of amide derivatives. The transformation relies on the use of nickel catalysis and proceeds using sterically hindered tri- and tetrasubstituted olefins to give products containing quaternary centers. The resulting polycyclic or spirocyclic products can be obtained in good yields. Moreover, a diastereoselective variant of this methodology demonstrates its value for accessing adducts bearing vicinal, highly substituted sp3 stereocenters. Our results demonstrate that amide derivatives can be used as building blocks for the assembly of complex scaffolds.

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(Carbo)nucleoside derivatives constitute an important class of pharmaceuticals, yet there are only few convergent methods to access new analogues. In this communication, we report the first synthesis of thymine, uracil and 5-fluorouracil substituted diester donor-acceptor cyclopropanes and their use in the indium-and tin-catalyzed [3+2] annulations with aldehydes, ketones and enol ethers. The obtained diester products could be easily decarboxylated and reduced to the corresponding alcohols. The method gives access to a broad range of new (carbo)nucleoside analogues in only four-five steps and will be highly useful for the synthesis of libraries of bioactive compounds.The natural nucleosides constitute the building blocks of DNA and RNA. The interaction of enzymes and other biomolecules with nucleosides is essential for the regulation of genetic expression and cell replication. Therefore, the nucleoside scaffold constitutes a privileged structure in medicinal chemistry (Figure 1). [1] In addition to bioactive natural products, such as the antiviral and antibiotic aristeromycin (1), more than 45 FDA approved drugs are nucleoside analogues. Besides only slightly modified analogues, such as cytarabine (2) and telbivudine (3), more elaborated compounds derived from thymine have been successful, such as the carbonucleoside stavudine (4), the anti-HIV front drug azidothymidine (5) or the fluorinated floxuridine (6). Nevertheless, resistances are emerging in viral infections, and less toxic anticancer agents would be highly desirable, asking for the development of new bioactive nucleoside analogues.The synthesis of nucleoside analogues has been the focus of intensive effort since several decades. [2] Nevertheless, most methods are based on a linear approach involving first the synthesis of a ribose analogue followed by introduction of the nucleobase, either via formation of the C-N bond using a substitution reaction from an acetate I (Vorbrüggen reaction) [2b] or a condensation reaction from an aminoglycoside II [2a] (Scheme 1, A). This approach is efficient if the targeted analogue is similar to a natural ribose derivative, but can involve a long multi-step sequence if a more elaborate scaffold is desired. [3] This is particularly true for carbonucleoside analogues, for which elegant synthetic approaches involving ring-closing metathesis, [3a] Pauson-Khand [3b] or desymmetrization starting from cyclopentadiene and proceeding via diols, [3c-e] Vince's lactam [3f-g] or nitroso cycloaddition reactions [3h] have been developed. Our group has introduced the use of imide-substituted diester cyclopropanes in [3+2] annulation reactions. [4] With this new class of donor-acceptor cyclopropanes, [5] access to intermediates of type II became possible (Scheme 2, B). Nevertheless, the efficiency of the annulation process was mitigated by the necessary removal of the phthalimide group followed by DNA-base construction, which would add several steps to the synthetic sequence. Furthermore, the deprotection of the...

One-pot reactions that combine non-enzymatic and biocatalytic transformations represent an emerging strategy in chemical synthesis. Some of the most powerful chemoenzymatic methodologies, although uncommon, are those that form a carbon-carbon (C-C) bond and a stereocenter at one of the reacting carbons, thereby streamlining traditional retrosynthetic disconnections. Here we report the one-pot, chemoenzymatic conversion of amides to enantioenriched alcohols. This transformation combines a nickel-catalyzed Suzuki-Miyaura coupling of amides in aqueous medium with an asymmetric, biocatalytic reduction to provide diarylmethanol derivatives in high yields and enantiomeric excesses. The synthetic utility of this platform is underscored by the formal syntheses of both antipodes of the pharmaceutical orphenadrine, which rely on ketoreductase enzymes that instill complementary stereoselectivities. We provide an explanation for the origins of stereoselectivity based on an analysis of the enzyme binding pockets.

Efficient methods for the convergent synthesis of (poly)cyclic scaffolds are urgently needed in synthetic and medicinal chemistry. Herein, we describe new annulation reactions of thioalkynes with phthalimide-substituted donor-acceptor cyclopropanes, which gave access to highly substituted cyclopentenes and polcyclic ring systems. With silyl-thioalkynes, Lewis acid catalysed (3+2) annulation reaction with DAcyclopropanes took place affording 1-thio-cyclopenten-3-amines. On the other hand, an unprecedented polycyclic compound was formed with alkyl-thioalkynes through a reaction pathway directly involving the phthalimide group. The two transformations proceeded in good yield and tolerated a large variety of functional groups.

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