Copper(II)-Catalyzed Amination of Aryl Chlorides in Aqueous Ammonia.

Anilines are ubiquitous in bio-active compounds and their synthesis can be achieved via metal-catalyzed cross-coupling reactions involving aryl halides. We describe an unusual, yet simple, CuII-catalyzed system for the amination of aryl chlorides in pure aqueous ammonia with 2.5 mol % catalyst loading under non-inert conditions. Different from previous systems, the reaction proceeds even without an additional organic solvent. Copper(II) sulfate in combination with 4,7-dimethoxy-1,10-phenanthroline enabled the amination of several aryl chlorides containing electron-neutral, -donating and -withdrawing groups to the corresponding anilines with good to excellent yields. The upscaling potential of the procedure has been shown by the synthesis at 50 mmol scale. The reaction proceeds as one of the rare cases of a CuII-assisted coupling, in contrast to the typical CuI-CuIII intermediates postulated for most Ullmann-type coupling reactions. The copper(II) center allows for a nucleophilic substitution pathway, enabled by the deprotonation of coordinated ammonia.

Transfer Hydrocyanation of α- and α,ß-Substituted Styrenes Catalyzed by Boron Lewis Acids.

A straightforward gram-scale preparation of cyclohexa-1,4-diene-based hydrogen cyanide (HCN) surrogates is reported. These are bench-stable but formally release HCN and rearomatize when treated with Lewis acids. For BCl3 , the formation of the isocyanide adduct [(CN)BCl3 ]- and the corresponding Wheland complex was verified by mass spectrometry. In the presence of 1,1-di- and trisubstituted alkenes, transfer of HCN from the surrogate to the C-C double bond occurs, affording highly substituted nitriles with Markovnikov selectivity. The success of this transfer hydrocyanation depends on the Lewis acid employed; catalytic amounts of BCl3 and (C6 F5 )2 BCl are shown to be effective while B(C6 F5 )3 and BF3 ⋅OEt2 are not.

Palladium-Catalyzed Three-Component Reaction of Dihydrosilanes and Vinyl Iodides in the Presence of Alcohols: Rapid Assembly of Silyl Ethers of Tertiary Silanes.

A one-pot reaction that directly converts dihydrosilanes into silyl ethers of tertiary silanes is reported. Under palladium catalysis, one Si-H bond of the dihydrosilane formally engages in C(sp3 )-Si bond formation with a vinyl iodide while the other Si-H bond is transformed into a silyl iodide that undergoes facile alcoholysis with an alcohol. The C-C double bond is reduced in that process. This three-component reaction provides in a single synthetic operation an access to silyl ethers of functionalized and hindered alcohols. Several of those would otherwise be difficult to make but the intermediacy of a highly reactive silyl iodide even allows for tert-butanol to react at room temperature.

Cyclohexa-1,3-diene-based dihydrogen and hydrosilane surrogates in B(C6F5)3-catalysed transfer processes.

The cyclohexa-1,3-diene motif is introduced as an equally effective alternative to the cyclohexa-1,4-diene platform in B(C6F5)3-catalysed transfer processes. The transfer hydrogenation of alkenes is realised with α-terpinene and the related transfer hydrosilylation is achieved with 5-trimethylsilyl-substituted cyclohexa-1,3-diene. Both yields and substrate scope are comparable with the prior systems.