Macrocyclic compounds are obtained in one step by the reaction of carbo-and heterocyclic dianions with bis-electrophiles, such as Me2SiCl2, Me2SnCl2, or PhPCl2. p-fert-Butylmethoxybenzene as starting material affords silacalix[4]arene 7. The most stable conformers of 7 are determined by force field calculations. A 1,3 alternate conformation in the crystal is revealed by X-ray structure analysis for the heterocyclic silacalix[4]arenes 3a and 3c, while 3b shows a partial cone conformation. The ability of the macrocycles to extract metal ions from the aqueous phase is investigated in competition experiments. The tested macrocycles extract metal ions, however, with less affinity than crown ethers.Bu7 in hexane complete deprotonation at the 2-and 5-position is achieved. Slow addition of a solution of Me2-SiCl2 in hexane gave the macrocyclic tetramers 3a-c8 and hexamers 4a,b in yields up to 35% (Scheme 2). The Results and DiscussionThe facile deprotonation of thiophene, fur an, and JV-methylpyrrole in the 2or 5-position by a strong base

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Readily available starting materials can be used to prepare silicon‐bridged macrocycles of different ring sizes by deprotonation and reaction with Me2SiCl2. While heterocycles such as furan or thiophene gave sila[14]‐ and sila[16]phanes, para‐(tert‐butyl)methoxybenzene afforded the first silacalix‐[4]arene 1.

Linear and cyclic oligomers of Me2Ge-bridged n-systems have been obtained by the reaction of carbo-and heterocyclic anions and dianions with MezGeCl2. The spectroscopic properties of the new compounds are compared with dnalogous carbon-and Me,Si-bridged n-systems.The clean reaction of carbanions with Me2SiC12 has been used by usrll and other groups [2] for the synthesis of dimeric and oligomeric n-systems bridged by Me2% units. We report here the extension of the synthetic route to Me2Ge-bridged n-systems and compare their synthesis and properties with Me2Si-and carbon-bridged compounds.The reaction of lithiated heterocycles, such as furan, thiophene or N-methylpyrrole with Me2GeC12 gave Me2Ge-bridged dimers 2L3] in good yield. Deprotonation of the heterocycles with nBuLilTMEDNKOtBu led to the formation of 2,5-dianions which in turn were allowed to react with Me2GeC12 to yield a mixture of linear ~ligomers [~]. Macrocyclic products, as formed in the reaction with Me2SiC1&'] were not detected, although the fast reaction of the slowly added Me2GeClz with carbanions and the limited solubility of the heterocyclic dianions in hexane solution should favour their formation [5].An alternative route for the synthesis of cyclic oligomers uses 2a-c. These are cleanly deprotonated at the 5-and 5 ' -positions upon treatment with BuLilTMEDA. The resulting dianions were trapped with TMSCI, and NMR spectra of the crude reaction mixtures confirmed the complete formation of dianions. Here again, the reaction of stoichiometric amounts Me2GeC12 with the dianions of 2a and b resulted in the formation of a mixture of linear oligomers as the major product. In the case of Zc, however, the macrocyclic tetramer 4 was isolated in small amounts. The simple 'H and I3C-NMR spectra of 4 indicate the unrestricted mobility of the pyrrole rings in solution on the NMR time scale. The incorporation of four germanium atoms is confirmed by the complex isotope pattern of the molecular ion in the mass spectra. Methoxy-directed orth~-lithiation[~l of 5 or 8 and subsequent reaction with Me2GeCI2 yielded compounds 6 and 9 in good yield. Both compounds were cleanly lithiated to dianions with BuLi/TMEDA, as confirmed by trapping with TMSCl. The reaction of the dianion of 9 with Me2. GeCI2 gave linear oligomers exclusively, whereas the reaction of 6 and Me2GeC12 yielded heterocalix[4]arene 11 in