- Coplanar tetracyclic π-excess σ2P ligands
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The acid-catalyzed reactions of 5-methyl-2-phosphanylaniline (1) with dialdehydes were studied. Whereas the reaction with glyoxal provides a mixture of two 1H-1,3-benzazaphospholes, 2 and 3, by concomitant reduction of a CHO group and C-C bond cleavage, respectively, the reaction with o-phthalic dicarbaldehyde provided in excellent yield the tetracyclic planar benzazaphosphole 4, which was characterized by crystal structure analysis. The active hydrogen atoms, delivered by aromatization of a dihydrobenzazaphosphole intermediate, forms an N-CH2 bridge by reductive N-alkylation. Pyridine-2,6-dicarbaldehyde reacts analogously but not chemoselectively and, thus, gives two isomers 5 and 6. Condensation with pyridine-2,6-dicarbaldehyde afforded the bis(benzazaphosphole)pyridine pincer ligand 7, but along with 2-(benzazaphospholyl)-6-tolylpyridine (8) by partial P-C bond cleavage. The high upfield 31P NMR chemical shift of 4 compared to those of normal benzazaphospholes indicates it to be a particularly π-rich σ2P ligand. Aromatization-driven acid-catalyzed condensations of the N,P-diprimary compound 1 with dialdehydes are coupled with hydrogen transfer reactions. With glyoxal and pyridine-2,6-dicarbaldehyde this gives rise to side products, but with o-C6H4(CHO)2, high yields of 4 are obtained. π-Delocalization through the coplanar aryl rings causes high π-density at the phosphorus atom.
- Niaz, Basit,Iftikhar, Fatima,Kindermann, Markus K.,Jones, Peter G.,Heinicke, Joachim
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p. 4220 - 4227
(2013/09/12)
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- Silver-catalyzed formal inverse electron-demand diels-alder reaction of 1,2-diazines and siloxy alkynes
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A highly effective silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes has been developed. The reactions provide ready access to a wide range of siloxy naphthalenes and anthracenes, which are formed in good to high yields, under mild reaction conditions, using low catalyst loadings.
- Tuerkmen, Yunus E.,Montavon, Timothy J.,Kozmin, Sergey A.,Rawal, Viresh H.
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supporting information; experimental part
p. 9062 - 9065
(2012/07/14)
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- Synthesis of 2-Aryl-2,3-dihydro-oxazolopyrrolopyridin-5-one and 2-Aryl-2,3-dihydro-oxazolopyrrolopyridin-5-one
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A variety of 2-aryl-2,3-dihydro-oxazolopyrrolopyridin-5-one and 2-aryl-2,3-dihydro-oxazolopyrrolopyridin-5-one were prepared. The absolute configuration of the chiral centers were studied thoroughly from which the structural and stereoformulea of these compounds were deduced by using nmr and microanalysis technique.
- Makki, Mohamad S. I.,Samarkandy, Abdul-Rahim A.,Kabuli, Rida A.,Hewlins, M. J. E.
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