Pyrrole Synthesis via Allylic sp<sup>3</sup> C−H Activation of Enamines Followed by Intermolecular Coupling with Unactivated Alkynes
作者:Souvik Rakshit、Frederic W. Patureau、Frank Glorius
DOI:10.1021/ja104305s
日期:2010.7.21
A conceptually novel pyrrole synthesis is reported, efficiently merging enamines and (unactivated) alkynes under oxidative conditions. In an intermolecular Rh catalyzed process, the challenging allylic sp(3) C-H activation of the enamine substrates is followed by the cyclization with the alkyne (R(3) = CO(2)R). Alternatively, in some cases (R(3) = CN), the enamine can be utilized for a vinylic sp(2)
Nickel-Catalyzed Asymmetric Transfer Hydrogenation of Olefins for the Synthesis of α- and β-Amino Acids
作者:Peng Yang、Haiyan Xu、Jianrong Steve Zhou
DOI:10.1002/anie.201407744
日期:2014.11.3
The field of asymmetric (transfer) hydrogenation of prochiral olefins has been dominated by noble metal catalysts based on rhodium, ruthenium, and iridium. Herein we report that a simple nickel catalyst is highly active in the transfer hydrogenation using formic acid. Chiral α‐ and β‐amino acid derivatives were obtained in good to excellent enantioselectivity. The key toward success was the use of
A compound represented by the following general formula (I):
[wherein R
1
represents hydrogen atom, or an alkyl group, R
2
represents a hydroxyalkyl group, or a triarylmethyloxyalkyl group, or R
1
and R
2
combine together to represent —C(R
3
)(R
4
)— (R
3
and R
4
represent hydrogen atom, an alkyl group, or hydroxyl group, or R
3
and R
4
may combine together to represent oxo group), or —C(R
5
)(R
6
)—O—C(R
7
)(R
8
)— (R
5
to R
8
represent hydrogen atom, an alkyl group, or hydroxyl group, or R
5
and R
6
may combine together to represent oxo group, and R
7
and R
8
may combine together to represent oxo group); Ar
1
to Ar
4
independently represent an aryl group (the aryl group may have 1 to 5 of the same or different substituents), *1 to *4 indicate asymmetric carbons, and configurations are cis between *1 and *2, cis between *3 and *4, and trans between *2 and *3]. An optically active phosphine ligand which can be easily synthesized and gives a transition metal complex showing superior asymmetric catalyst activity is provided.
The rhodium-catalyzedasymmetrichydrogenation of various β-dehydroamino acid derivatives to give optically active β-amino acids has been examined. Chiral monodentate 4,5-dihydro-3H-dinaphthophosphepines, which are easily tuned and accessible in a multi-10-g scale, have been used as ligands. The enantioselectivity is largely dependent on the nature of the substituent at the phosphorous atom and on
Synthesis of β-Amino Acid Derivatives via Copper-Catalyzed Asymmetric 1,4-Reduction of β-(Acylamino)acrylates
作者:Yan Wu、Shan-Bin Qi、Fei-Fei Wu、Xi-Chang Zhang、Min Li、Jing Wu、Albert S. C. Chan
DOI:10.1021/ol200287z
日期:2011.4.1
A new set of reaction conditions has been established to facilitate the copper-catalyzed enantioselective 1,4-reduction of β-(acylamino)acrylates toward a selection of β-alkyl-β-amino acid derivatives in high yields and with uniformly high ee values (up to 99%) irrespective of the use of (E)- or (Z)-substrates.