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Boron functional groups are often introduced in place of aromatic carbon-hydrogen bonds to expedite small-molecule diversification through coupling of molecular fragments.sup.1-3. Current approaches based on transition-metal-catalysed activation of carbon-hydrogen bonds are effective for the borylation of many (hetero)aromatic derivatives.sup.4,5 but show narrow applicability to azines (nitrogen-containing aromatic heterocycles), which are key components of many pharmaceutical and agrochemical products.sup.6. Here we report an azine borylation strategy using stable and inexpensive amine-borane.sup.7 reagents. Photocatalysis converts these low-molecular-weight materials into highly reactive boryl radicals.sup.8 that undergo efficient addition to azine building blocks. This reactivity provides a mechanistically alternative tactic for sp.sup.2 carbon-boron bond assembly, where the elementary steps of transition-metal-mediated carbon-hydrogen bond activation and reductive elimination from azine-organometallic intermediates are replaced by a direct, Minisci.sup.9-style, radical addition. The strongly nucleophilic character of the amine-boryl radicals enables predictable and site-selective carbon-boron bond formation by targeting the azine's most activated position, including the challenging sites adjacent to the basic nitrogen atom. This approach enables access to aromatic sites that elude current strategies based on carbon-hydrogen bond activation, and has led to borylated materials that would otherwise be difficult to prepare. We have applied this process to the introduction of amine-borane functionalities to complex and industrially relevant products. The diversification of the borylated azine products by mainstream cross-coupling technologies establishes aromatic amino-boranes as a powerful class of building blocks for chemical synthesis. Selective borylation of azines--nitrogen-containing aromatic heterocycles used in the synthesis of many pharmaceuticals--is made possible by forming a radical from an aminoborane using a photocatalyst., Author(s): Ji Hye Kim [sup.1] , Timothée Constantin [sup.1] , Marco Simonetti [sup.1] , Josep Llaveria [sup.2] , Nadeem S. Sheikh [sup.3] , Daniele Leonori [sup.1] Author Affiliations: (1) Department [...]

Tertiary alcohols are displaced with a nitrogen nucleophile with stereoinversion and with high selectivity over less substituted alcohols, providing complementarity to the S.sub.N2 reaction and efficient access to nitrogenous marine terpenoids. Tertiary alcohols as targets for stereoinversion This paper describes a new method for the stereoselective displacement of tertiary alcohols with a nitrogen nucleophile. The procedure leads to inversion of stereochemistry and enables short, stereo- and chemoselective syntheses of naturally occurring terpenoid isonitriles and amines. Displacement does not occur with secondary and primary substrates, representing a reversal of substitution demand compared to the S.sub.N2 reaction (bimolecular nucleophilic substitution), a well-known chemical transformation commonly used to join two smaller molecules together into a larger molecule or to exchange one functional group for another. The authors suggest that this new approach could lead to the development of other stereoinversion reactions of tertiary alcohols and stimulate further progress in carbocation chemistry. The S.sub.N2 reaction (bimolecular nucleophilic substitution) is a well-known chemical transformation that can be used to join two smaller molecules together into a larger molecule or to exchange one functional group for another. The S.sub.N2 reaction proceeds in a very predictable manner: substitution occurs with inversion of stereochemistry, resulting from the 'backside attack' of the electrophilic carbon by the nucleophile. A significant limitation of the S.sub.N2 reaction is its intolerance for tertiary carbon atoms: whereas primary and secondary alcohols are viable precursor substrates, tertiary alcohols and their derivatives usually either fail to react or produce stereochemical mixtures of products.sup.1,2,3. Here we report the stereochemical inversion of chiral tertiary alcohols with a nitrogenous nucleophile facilitated by a Lewis-acid-catalysed solvolysis. The method is chemoselective against secondary and primary alcohols, thereby complementing the selectivity of the S.sub.N2 reaction. Furthermore, this method for carbon-nitrogen bond formation mimics a putative biosynthetic step in the synthesis of marine terpenoids.sup.4 and enables their preparation from the corresponding terrestrial terpenes. We expect that the general attributes of the methodology will allow chiral tertiary alcohols to be considered viable substrates for stereoinversion reactions., Author(s): Sergey V. Pronin [sup.1] , Christopher A. Reiher [sup.1] , Ryan A. Shenvi [sup.1] Author Affiliations: (1) Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, [...]

Author(s): Ming Joo Koh [1]; Thach T. Nguyen [1]; Jonathan K. Lam [2]; Sebastian Torker [1]; Jakub Hyvl [2]; Richard R. Schrock [2]; Amir H. Hoveyda (corresponding author) [1] The [...]

Researchers have come up with a biochemical pathway that converts carbon dioxide into useful organic compounds more efficiently than plants can. A team led by Tobias Erb at the Max [...]