ABSTRACT:In recent years a significant progress has been made for the carboxylation of aryl and benzyl halides with CO 2 , becoming covenient alternatives to the use of stoichiometric amounts of well-defined metal species. Still, however, most of these processes require the use of pyrophoric and air-sensitive reagents and the current methods are mostly restricted to organic halides. Therefore, the discovery of a mild, operationally-simple alternate carboxylation, that occurs with a wide substrate scope employing readily available coupling partners will be highly desirable, hence improving the flexibility in catalytic design while increasing our ever-growing synthetic arsenal. Herein, we report a new protocol that deals with the development of a synergistic activation of CO 2 and a rather challenging activation of inert C(sp 2 )−O and C(sp 3 )−O bonds derived from simple and cheap alcohols, a previously unrecognized opportunity in this field. This unprecedented carboxylation event is characterized by its simplicity, mild reaction conditions, remarkable selectivity pattern and an excellent chemoselectivity profile using air-, moisture-insensitive and easy-to-handle nickel precatalysts without the use of any sensitive metal species. Our results render our method a powerful alternative, practicality and novelty aside, to commonly used organic halides as counterparts in carboxylation protocols. Furthermore, this study shows, for the first time, that traceless directing groups allow for the reductive coupling of substrates without extended π-systems, a typical requisite in many C−O bond-cleavage reactions. Taking into consideration the limited knowledge in catalytic carboxylative reductive events, inert C−O bond-cleavage and the prospective impact of providing a new tool for accessing valuable carboxylic acids, we believe this work opens up new vistas and allows new tactics in reductive coupling events.

A novel Ni-catalyzed carboxylation of benzyl halides with CO(2) has been developed. The described carboxylation reaction proceeds under mild conditions (atmospheric CO(2) pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.

In this Communication, the enantiomeric excess reported for the hydrogenation of N-(3,4-dihydronaphthalen-2-yl)acetamide was incorrect. An unnoticed impurity contained in the racemic sample led to the use of an inappropriate HPLC method for the determination of the optical purity. Reanalyzing the sample with a correct HPLC method (Chiralcel OD-H, hexanes/isopropyl alcohol (95:5), 1.0 mL min À1 , 210 nm, t(À) = 23.5 min, t(þ) = 27.5 min) [1] showed that the reduction product was obtained in only 9 % ee. The authors apologize for this error.

The stereodivergent ring-opening of 2-phenyl oxazaphospholidines with alkyl lithium reagents is reported. N-H oxazaphospholidines derived from both (+)-cis-1-amino-2-indanol and (-)-norephedrine provide inversion products in a highly stereoselective process. In contrast, N-Me oxazaphospholidines yield ring-opening products with retention of configuration at the P center, as previously reported by Jugé and co-workers. As a result, from a single amino alcohol auxiliary, both enantiomers of key P-stereogenic intermediates could be synthesized. Theoretical studies of ring-opening with model oxazaphospholidines at the DFT level have elucidated the streochemical course of this process. N-H substrates react in a single step via preferential backside S(N)2@P substitution with inversion at phosphorus. N-methylated substrates react preferentially via a two-step frontside S(N)2@P, yielding a ring-opened product in which the nucleophilic methyl binds to P with retention of configuration. DFT calculations have shown that the BH3 unit is a potent directing group to which the methyl lithium reagent coordinates via Li in all the reactions studied.

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We report a BF3-mediated direct alkynylation of pyridines at C(2) by using a variety of alkynyllithium reagents (oxidative cross-coupling). Moreover, we have developed a novel transition-metal-free cross-coupling method between alkylmagnesium reagents and 4-substituted pyridines, such as isonicotinonitrile and 4-chloropyridine, by employing BF3⋅OEt2 as a promoter. The combination of these methods enabled us to efficiently prepare a range of di-, tri-, and tetrasubstituted pyridines.

In dieser Zuschrift wurde für die Hydrierung von N-(3,4-Dihydronaphthalin-2-yl)acetamid ein falscher Enantiomerenüberschuss angegeben. Eine nicht erkannte Verunreinigung in der racemischen Probe führte dazu, dass die optische Reinheit nicht angemessenen HPLC-Methode bestimmt wurde. Eine erneute Analyse der Probe mit einer geeigneten HPLC-Methode (Chiralcel OD-H, Hexan/Isopropylalkohol 95:5, 1.0 mL min À1, 210 nm, t(À) = 23.5 min, t(þ) = 27.5 min) [1] belegt, dass das Reduktionsprodukt mit nur 9 % ee erhalten wurde. Die Autoren entschuldigen sich für diesen Fehler.

Herein, we report a practical two‐step synthetic route to α‐arylpyrrolidines through Suzuki–Miyaura cross‐coupling and enantioselective copper‐catalyzed intramolecular hydroamination reactions. The excellent stereoselectivity and broad scope for the transformation of substrates with pharmaceutically relevant heteroarenes render this method a practical and versatile approach for pyrrolidine synthesis. Additionally, this intramolecular hydroamination strategy facilitates the asymmetric synthesis of tetrahydroisoquinolines and medium‐ring dibenzo‐fused nitrogen heterocycles.