Synthesis and Structural Peculiarities of Homeomorphic Phosphorus Bridgehead Macrobicyclic Compounds and Novel Dioxaphospha[3.1.1.]p,m,p-cyclophanes Ingmar Bauer,* [a] Roland Frˆhlich, [b] Albina Yu. Ziganshina, [c] Alexander V. Prosvirkin, [c] Margit Gruner, [a] Ella Kh. Kazakova, [c] and Wolf D. Habicher* [a] Abstract: The double-capping reaction of p,m,p-trinuclear diphenol 4 with PCl 3 affords the three homeomorphic iso- mers 5 ± 7 of a phosphite macrobicyclic compound in low yields. X-ray struc- tures of out,out-isomer 5 and in,in-iso- mer 6 show very flat macrobicyclic structures with P ± P distances of 4.9 ä and 4.5/5.3 ä (two conformers), respec- tively. The main product of the reaction, however, appears to be diphosphite 8, which contains two dioxaphos- pha[3.1.1.]p,m,p-cyclophane subunits. The structural peculiarities of 8 were studied after subsequent oxidation to the corresponding phosphate 12. At room temperature the free rotation either of the para-phenylene rings and the meta-phenylene ring in the macro- cyclic moieties are hindered as could be demonstrated by means of NOESY measurements. The latter occupies an angled position in respect to the macro- cyclic plane. This leads to the existence of conformational isomers due to differ- ent relative positions of the meta-phe- nylene ring to the P-OR substituent (cis ,trans). We could isolate the cis ,cis- isomer of 12 and establish its structure by X-ray diffraction. Keywords: cage compounds ¥ cyclo- phanes ¥ isomers ¥ phosphates ¥ structure elucidation Introduction Phosphorus-containing macrocycles have potential applica- tions in supramolecular and synthetic organic chemistry. [1] The trivalent phosphorus atom can for instance function as donor site for soft transition metals especially in their low valent states. This makes them interesting as ligands for transition- metal-catalyzed reactions such as Heck reaction, hydrofor- mylation, homogenous catalytic hydration, Suzuki coupling, Sonogashira coupling, and others which occupy a more and more important place in standard organic synthesis. The design of the involved ligand systems to optimize catalytic reactions in terms of yield, turnover number and selectivity is therefore an extensively investigated area in organic chem- istry. [2] Trivalent phosphorus atoms easily undergo oxidation reaction to give pentavalent species such as phosphoryl moieties. In those compounds the phosphoryl oxygen can function as a hard donor atom, which upon its integration into macrocyclic systems may be used for metal complexation and for molecular recognition of hydrogen-donating substrates, among them also biologically interesting compounds such as amino acids. [3] Moreover the trivalent P atom offers a point of attachment for the introduction of additional components with special functions to the macrocylic cores. Only a few macrobicyclic systems with P-bridgehead atoms have been reported up to now. [4±13] In addition, some medium- sized P-bridgehead bicyclic compounds have been synthesized and investigated. [14±17] All of these compounds show the interesting structural feature of in/out isomerism. [18] In the case of larger trivalent P-bridgehead macrobicyclic com- pounds this opens up the chance for reactions on the ™inner wall∫ of the cage by use of the well-defined geometry of in-P lone pairs. Various methods can be applied for the synthesis of macrobicyclic compounds. [18b] The double-capping and tri- pod-capping reaction should not be very favored. Five components have to be assembled in the right manner under [a] Doz. Dr. W.-D. Habicher, Dr. I. Bauer, Dr. M. Gruner Institute of Organic Chemistry Technical University of Dresden Mommsenstr. 13, 01062 Dresden (Germany) Fax: ( 49)351-463-34093 E-mail: wolf.habicher@chemie.tu-dresden.de [b] Dr. R. Frˆhlich Institute of Organic Chemistry, University M¸nster Corrensstrasse 40, 48149 M¸nster (Germany) Fax: ( 49)251-83-39772 E-mail: frohlic@nwz.uni-muenster.de [c] Dr. A. Yu. Ziganshina, Dr. A. V. Prosvirkin, Prof. E. Kh. Kazakova A. E. Arbuzov Institute of Organic and Physical Chemistry KSC RAS Arbusov str. 8, 420088 Kazan, Russian Federation Fax: ( 7)8432-752253 E-mail: az@iopc.knc.ru FULL PAPER ¹ 2002 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim 0947-6539/02/0824-5622 $ 20.00+.50/0 Chem. Eur. J. 2002, 8, No. 24 5622