Homoleptic lanthanide
complex Y[N(TMS)2]3 is an efficient homogeneous
catalyst for the hydroboration reduction
of secondary amides and tertiary amides to corresponding amines. A
series of amides containing different functional groups such as cyano,
nitro, and vinyl groups were found to be well-tolerated. This transformation
has also been nicely applied to the synthesis of indoles and piribedil.
Detailed isotopic labeling experiments, control experiments, and kinetic
studies provided cumulative evidence to elucidate the reaction mechanism.
A lanthanide-catalyzed intermolecular hydroamination of 2-alkynylbenzonitriles with secondary amines has been disclosed, providing a streamlined access to a range of aminoisoindoles in moderate to excellent yields. The salient features of this reaction include high bond-formation efficiency, mild reaction conditions, 100 % atomic efficiency and good functional group tolerance. This methodology has also been successfully applied to the construction of other nitrogen-containing compounds, such as 5 H-imidazo[2,1-a]isoindoles and isoquinolines. A plausible mechanism for the formation of aminoisoindoles involving initial N-H activation by a lanthanide complex followed by C≡N insertion into a Ln-N bond to form an amidinate lanthanide intermediate, which undergoes the cyclization is proposed.
The first example of the Pd-catalyzed addition of organoboron
reagents
to dinitriles, as an efficient means of preparing 2,5-diarylpyrroles
and 2,6-diarylpyridines, has been discussed here. Furthermore, the
highly selective carbopalladation of dinitriles with organoboron reagents
to give long-chain ketonitriles has been developed as well. Based
on the broad scope of substrates, excellent functional group tolerance,
and use of commercially available substrates, the Pd-catalyzed addition
reaction of arylboronic acid and dinitriles is expected to be significant
in future synthetic procedures.
We report herein a rare‐earth‐metal‐catalyzed insertion of a 2‐pyridine C(sp2)−H bond into an intramolecular unactivated vinyl bond. This reaction provides streamlined access to a range of azaindolines in moderate to excellent yields. The salient features of this reaction include simple and mild reaction conditions, 100% atom efficiency, and wide substrate scope. This methodology is also used to construct other nitrogen‐containing compounds such as naphthyridine derivatives. A plausible mechanism for the formation of azaindolines involving initial C−H bond activation by the lanthanide complex followed by C=C insertion into a Ln−C bond to form an alkyl lanthanide species that subsequently undergoes cyclization is proposed.
Palladium-catalyzed base-free addition of aryltriolborates to aldehydes has been developed, leading to a wide range of carbinol derivatives in good to excellent yields. The efficiency of this transformation was demonstrated by compatibility with a wide range of functional groups. The present synthetic route to carbinol derivatives could be readily scaled up to gram quantity without difficulty. Thus, this method represents a simple and practical procedure to access carbinol derivatives.
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