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Synthetic access to 6,7-dihydro-4 H -pyrazolo[5,1- c ][1,4]oxazines has been achieved in 3–4 steps from commercially available pyrazoles. Optimization of a protected hydroxyethyl group on N1 enabled the regiocontrolled construction of pyrazole-5-aldehydes in high yields; subsequent deprotection and reduction generated fused heterocyclic scaffolds bearing multiple substitution patterns. Moreover, the intermediate pyrazole lactols were shown to be versatile synthetic building blocks. [ABSTRACT FROM AUTHOR]

A four-step protocol for the synthesis of pyrazolo[1,5-a]pyrazines has been developed. Commercially available pyrazoles were alkylated and formylated in a regiocontrolled manner to give pyrazole-5-aldehydes bearing 2,2-dialkoxyethyl substitution on N-1. Efficient conditions for the subsequent deprotection and cyclization of these intermediates allowed access to pyrazolo[1,5-a]pyrazines with multiple substitution patterns. The versatility of the pyrazole-5-aldehyde intermediates was further demonstrated through a deprotection and double-reductive amination sequence to give 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazines. [ABSTRACT FROM AUTHOR]

Arylacetonitriles are versatile building blocks for the construction of heterocyclic scaffolds in medicinal chemistry. These intermediates are able to engage in a variety of synthetic transformations, giving rise to diverse biologically active structures. This digest focuses on recent applications of this synthetic methodology by drug discovery teams across several disease areas, with an emphasis on different reaction types. [ABSTRACT FROM AUTHOR]

A practical method for the regiocontrolled synthesis of substituted quinoline-4-carboxylic acids is described. Solubility differences between the product quinoline regioisomers enable their facile separation, thus avoiding any challenging chromatographic purifications and allowing access to highly substituted quinoline compounds in three steps from commercially available anilines. [ABSTRACT FROM AUTHOR]

A two-stepprotocol has been developed for the introduction ofcyanomethylene groups to metalated aromatics through the intermediacyof substituted isoxazoles. Apalladium-mediated cross-coupling reaction was used to introduce theisoxazole unit, followed by release of the cyanomethylene functionunder thermal or microwave-assisted conditions. The intermediate isoxazoleswere shown to be amenable to further functionalization prior to deprotectionof the sensitive cyanomethylene motif, allowing access to a wide rangeof aryl- and heteroaryl-substituted acetonitrile building blocks. [ABSTRACT FROM AUTHOR]

The osmium-catalyzed oxidative cyclization of amino alcohol initiators formally derived from 1,4-dienes is an effective method for the construction of pyrrolidines, utilizing a novel reoxidant (4-nitropyridine N-oxide = NPNO). The cyclization of enantiopure syn- and anti-amino alcohols gives rise to enantiopure cis- and trans-2,5-disubstituted pyrrolidines, respectively. Moreover, the cyclization of bis-homoallylic amines bearing an exocyclic chelating group is shown to be a complementary method for trans-pyrrolidine formation. [ABSTRACT FROM AUTHOR]

Abstract: A new catalytic protocol has been established by using two separate oxidation reactions, catalysed by osmium, in tandem. Control of the pH and oxidation state of the metal is crucial in controlling this new sequence, which begins with a tethered aminohydroxylation reaction (Os(VIII) is active) and is followed by an oxidative cyclisation under acidic conditions (Os(VI) is active). The result of this work is an extremely quick route (five steps from commercially available materials) to complex THF rings containing an adjacent oxazolidinone and four new stereogenic centres. [Copyright &y& Elsevier]

A protocol for the coupling of potassium aryltrifluoroborate salts or heteroarylstannanes with a bromoisoxazole derivative is developed, and the products are deprotected under conventional or microwave‐assisted heating to form various aryl or hetarylacetonitriles, respectively. [ABSTRACT FROM AUTHOR]

The diagrams of the chemical equation for the synthesis of substituted quinoline-4-carboxylic derivatives is presented, with the methods of using solubility differences for the achievement of regiocontrol.

A transition‐metal‐free reductive hydroxymethylation reaction has been developed, enabling the preparation of tetrahydroisoquinolines bearing C4‐quaternary centers from the corresponding isoquinolines. Deuterium labelling studies and control experiments enable a potential mechanism to be elucidated which features a key Cannizzaro‐type reduction followed by an Evans–Tishchenko reaction. When isoquinolines featuring a proton at the 4‐position are used, a tandem methylation‐hydroxymethylation occurs, leading to the formation of 2 new C−C bonds in one pot. [ABSTRACT FROM AUTHOR]

A transition‐metal‐free reductive hydroxymethylation reaction has been developed, enabling the preparation of tetrahydroisoquinolines bearing C4‐quaternary centers from the corresponding isoquinolines. Deuterium labelling studies and control experiments enable a potential mechanism to be elucidated which features a key Cannizzaro‐type reduction followed by an Evans–Tishchenko reaction. When isoquinolines featuring a proton at the 4‐position are used, a tandem methylation‐hydroxymethylation occurs, leading to the formation of 2 new C−C bonds in one pot. [ABSTRACT FROM AUTHOR]