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Crystallographic Proof of Double Walden Inversion in Nucleophilic Substitution Reactions of Macrocyclic Cyclotriphosphazene Derivatives
Author(s) -
Beşli Serap,
Coles Simon J.,
Davies David B.,
Eaton Robert J.,
Hursthouse Michael B.,
Kıhç Adem,
Shaw Robert A.
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400745
Subject(s) - chemistry , nucleophile , moiety , nucleophilic substitution , aniline , stereochemistry , ring (chemistry) , pyrrolidine , substitution reaction , walden inversion , nucleophilic aromatic substitution , medicinal chemistry , organic chemistry , catalysis
Using X‐ray crystallography it is demonstrated unambiguously that a double Walden inversion reaction occurs for suc‐cessive nucleophilic substitution of the mono‐spiropropanoxy‐amino derivative of the cis ‐ansa‐macrocyclic cyclophosphazene compound N 3 P 3 [O(CH 2 ) 3 NH][O(CH 2 CH 2 O) 4 ]Cl 2 ( 3 ). The spiropropanoxyamino moiety enables groups above and below the plane of the N 3 P 3 ring to be distinguished. The first nucleophilic substitution of compound 3 with X – (e.g., X = 2‐naphthoxy) gives N 3 P 3 [O(CH 2 ) 3 NH][O(CH 2 CH 2 O) 4 ]XCl ( 4a ), which has a trans ‐ansa‐macrocyclic ring as a result of the inversion reaction, and then subsequent reaction of 4a with the same nucleophile gives N 3 P 3 [O(CH 2 ) 3 NH][O(CH 2 CH 2 O) 4 ]X 2 ( 5a ), in which the macrocyclic ring is cis ‐ansa again, but it is now on the opposite side of the N 3 P 3 ring from that of the starting material 3 as a result of the second inversion reaction. Structures stereochemically analogous to compound 5a were also obtained upon reaction with other monofunctional nucleophiles, such as phenol, pyrrolidine and aniline, to give compounds 5b , 5c and 5d , respectively, and with the difunctional nucleophile 2,2,3,3‐tetrafluorobutanediol to give the di‐ansa derivative 6 . Compound 3 was also sequentially treated with two different mononucleophiles — phenol and aniline — to give the unsymmetrically disubstituted compound 7 , in which the macrocyclic ring is also cis ‐ansa again and on the opposite side of the N 3 P 3 ring from that of the starting material, as a result of the double Walden inversion reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)