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Dendritic Ruthenium Porphyrins: A New Class of Highly Selective Catalysts for Alkene Epoxidation and Cyclopropanation
Author(s) -
Zhang JunLong,
Zhou HaiBing,
Huang JieSheng,
Che ChiMing
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020402)8:7<1554::aid-chem1554>3.0.co;2-r
Subject(s) - cyclopropanation , alkene , ruthenium , chemistry , cyclooctene , porphyrin , styrene , medicinal chemistry , catalysis , ethyl diazoacetate , polymer chemistry , organic chemistry , copolymer , polymer
Attachment of Fréchet‐type poly(benzyl ether) dendrons [G‐ n ] to carbonylruthenium( II ) meso ‐tetraphenylporphyrin ( 5 ) using covalent etheric bonds forms a series of dendritic ruthenium( II ) porphyrins 5 ‐[G‐ n ] m ( m =4, n =1, 2; m =8, n =0–2). The attachment was realized by treating the carbonylruthenium( II ) complex of 5,10,15,20‐ tetrakis(4′‐hydroxyphenyl)porphyrin or 5,10,15,20‐tetrakis(3′,5′‐dihydroxyphenyl)porphyrin with [G‐ n ]OSO 2 Me in refluxing dry acetone in the presence of potassium carbonate and [18]crown‐6. Complexes 5 ‐[G‐ n ] m were characterized by UV/Vis, IR, and NMR spectroscopy and mass spectrometry. All of the dendritic ruthenium porphyrins are highly selective catalysts for epoxidation of alkenes with 2,6‐dichloropyridine N ‐oxide (Cl 2 pyNO). The chemo‐ or diastereoselectivity increases with the generation number of the dendron and the number of dendrons attached to 5 , and complex 5 ‐[G‐2] 8 exhibits remarkable selectivity or turnover number in catalyzing the Cl 2 pyNO epoxidation of a variety of alkene substrates including styrene, trans ‐/ cis ‐stilbene, 2,2‐dimethylchromene, cyclooctene, and unsaturated steroids such as cholesteryl esters and estratetraene derivative. The cyclopropanation of styrene and its para ‐substituted derivatives with ethyl diazoacetate catalyzed by 5 ‐[G‐2] 8 is highly trans selective.