Mercuration of Schiff bases of substituted benzylideneanilines
摘要:
As part of an effort to investigate substituent effects on the intramolecular coordination between N and Hg, the mercuration of 36 substituted benzylideneanilines was studied. The structure characterization of the products by IR, H-1 NMR, C-13 NMR, and MS indicates that for all of the reactions examined, the mercury is directed to the ortho position of the N-phenyl ring or the para position of the N-phenyl ring when these sites are not occupied by a substituent. The position of the HgCl group in the mercurated product of N-(4-nitrobenzylidene)-beta-naphthylamine has been confirmed by single-crystal X-ray determination, which also provided circumstantial evidence for the existence of the N--> Hg intramolecular coordination with a four-membered ring. The possible mechanism of the reaction was proposed, in which the mercuration at the ortho position of the N-phenyl ring was facilitated by the imino moiety upon formation of a coordination complex with Hg(OAc)2 in the first step, followed by a subsequent electrophilic substitution at the ortho position of the N-phenyl ring. This reaction is different from the metalation of benzylideneanilines by transition metals, in which the metal atom is usually directed to the ortho position of the C-phenyl ring, and provides a new example of the so-called 'cyclometalation" reaction.
The effect of molecular planarity on crystal non-centrosymmetry in benzylidene–aniline derivatives
摘要:
In the title compound, N-(2-methoxyphenyl)-4-nitrobenzylideneamine, C(14)H(12)N(2)O(3), the two phenyl rings make a dihedral angle of 48.0 (2) degrees and the nitro group is at an angle of 6.5 (1) degrees with respect to its attached phenyl ring. In the crystal structure, molecules are related as centrosymmetric pairs through pi-pi interactions and are further connected through strong C[bond]H...O hydrogen bonds [C...O 3.4259 (17) A and C[bond]H...O 167 degrees ], forming molecular stacks along [100]. These stacks associate further through longer C[bond]H...O interactions, forming two-dimensional networks. In the c direction, there are only weak van der Waals interactions. The relationship between the molecular planarity and its centrosymmetry is also briefly described.
Ag-Catalyzed Asymmetric Mannich Reactions of Enol Ethers with Aryl, Alkyl, Alkenyl, and Alkynyl Imines
作者:Nathan S. Josephsohn、Marc L. Snapper、Amir H. Hoveyda
DOI:10.1021/ja049388e
日期:2004.3.1
An efficient catalytic and enantioselective method (up to >98% ee) for Mannich reactions between trimethylsilyl enol ethers derived from acetone and acetophenone and aryl, alkenyl, alkynyl, and alkyl imines is disclosed. A large variety of beta-amino ketones can be synthesized in the presence of 1-5 mol % AgOAc and an inexpensive and readily available amino acid-derived phosphine. All Ag-catalyzed
Unexpected Domino Synthesis of Complex Angular Naphthoimidazoles
作者:Gema Guedes、Matías López-Rodríguez、Angel G. Ravelo、Ana Estévez-Braun
DOI:10.1002/ejoc.201200625
日期:2012.10
Several disubstituted angularnaphthoimidazoles have been synthesized by a new domino reaction from (1,4-dimethoxynaphthalen-2-yl)amine (1) and imines (obtained from 1 and aromatic aldehydes) in the presence of Sc(OTf)3. A plausible pathway for the reaction involves attack of the nucleophilic amine on the imine and further reaction of the resulting intermediate by intramolecular cyclization with loss
Amine-catalyzed direct asymmetric Mannich-type reactions
作者:Wolfgang Notz、Kandasamy Sakthivel、Tommy Bui、Guofu Zhong、Carlos F Barbas
DOI:10.1016/s0040-4039(00)01908-0
日期:2001.1
Three chiral cyclic secondary amines are shown to be catalysts for the directasymmetricMannich-typereaction of acetone with a variety of preformed aldimines derived from o-anisidine. A simple one-pot three-component reaction procedure consisting of aldehyde, acetone, p-anisidine and an amine catalyst provides the corresponding β-amino ketones with 50–89% ee under very mild conditions.
A Highly Efficient and Practical Method for Catalytic Asymmetric Vinylogous Mannich (AVM) Reactions
作者:Emma L. Carswell、Marc L. Snapper、Amir H. Hoveyda
DOI:10.1002/anie.200603496
日期:2006.11.6
Efficient and Practical Ag-Catalyzed Cycloadditions between Arylimines and the Danishefsky Diene
作者:Nathan S. Josephsohn、Marc L. Snapper、Amir H. Hoveyda
DOI:10.1021/ja030033p
日期:2003.4.1
An efficient Ag-catalyzed method for asymmetric addition of the Danishefsky diene to various aryl imines to afford cycloadducts in > or =89% ee and > or =85% isolated yield is reported. Reactions are effected with 0.1-1 mol % catalyst (4 degrees C), and the chiral ligand is readily prepared from commercially available materials, including the inexpensive i-Leu. These catalytic asymmetric cycloadditions can be carried out without the use of solvent or with undistilled THF in air. A first generation supported chiral catalyst that effectively promotes the cycloaddition reaction and can be recycled (five cycles) is described.