Methods of enhancement of reactivity and selectivity of sodium borohydride for applications in organic synthesis

Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides—as well as primary ones—to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.

Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions.

PTP1B Inhibition and Antihyperglycemic Activity in the ob/ob Mouse Model of Novel 11-Arylbenzo[b]naphtho[2,3-d]furans and 11-Arylbenzo[b]naphtho[2,3-d]thiophenes

Molecular mechanics calculations were used to probe the conformational properties of a number of substituted phenanthrolines and their η3-allylpalladium complexes. Special attention was focused on phenanthrolines bearing chiral, terpene-derived, alkyl and alkenyl groups at C(2). Based upon these calculations, predictions could then be made regarding the suitability of the several ligands for use in asymmetric palladium-catalyzed substitution reactions of allylic acetates. Each of the substituted phenanthrolines was prepared by straightforward means. Use of these ligands in catalytic allylations gave results which were in good agreement with the calculation-based predictions. The highest levels of asymmetric induction were predicted and were obtained with a readily available 2-(2-bornyl)phenanthroline ligand 13. The results were compared with previously reported data obtained using other ligands. Overall, this work provides further indication of the potential utility of a combined calculational/experimenta...

Molecular Mechanics Predictions and Experimental Testing of Asymmetric Palladium-Catalyzed Allylation Reactions Using New Chiral Phenanthroline Ligands

The synthetic utility and potential power of the Diels–Alder (D–A) reaction in organic chemistry is evident. These significances have been extended to the synthesis of a plethora and wide variety of heterocyclic compounds via [4 + 2] cycloaddition reactions, the so called hetero Diels–Alder (HDA) reaction. In this work we try to focus on the scope and preparative synthetic applications of the HDA reaction as a key step in the total synthesis of natural products.

Recent applications of the hetero Diels–Alder reaction in the total synthesis of natural products

Le monoacetoxyborohydrure de sodium est le reactif le plus efficace pour la reduction etudiee

Charles F. Nutaitis

Papers

Regioselective 1,2-reduction of conjugated enones and enals with sodium monoacetoxyborohydride: preparation of allylic alcohols

Reduction of Monobenzylic Alcohols with Sodium Borohydride/Trifluoroacetic Acid

REDUCTION OF HETEROCYCLIC ALCOHOLS WITH SODIUM BOROHYDRIDE-TRIFLUOROACETIC ACID. PREPARATION OF bis-HETEROCYCLIC METHANES

Reduction of 1,3-azole and 1,3-benzazole carbinols with sodium borohydride-trifluoroacetic acid

Preparation of benzo[c][2,7]naphthyridines