Stannoles were prepared by 1,1-organoboration of bis(amino)di(l-alkynyl)tin compounds or di(l-alkynyl)tin dichlorides or -dibromides. Bulky amino groups are required in order to obtain bis(amino)tin dichlorides which do not exchange their ligands. These bis(amino)tin dichlorides were converted into bis(amino)di(lalkynyl)tin compounds, the precursors of the stannoles bearing amino groups at the tin atom. The stannoles bearing chloro or bromo ligands at the tin atom could also be obtained by exchange reactions of other stannoles with tin tetrachloride or -bromide, and, bearing Me 3 Si groups in the 2,5-positions, they were found to be surprisingly unstable with respect to elimination of tin dichloride or -dibromide, respectively. Di(methoxyethynyl)dimethyltin, Me 2 Sn(CsCOMe)2, and -germanium, Me2Ge(C»COMe) 2 , were treated with trialkylboranes. In the case of germanium, new germoles with methoxy groups in 2,5-positions were obtained. In the case of tin, the formation of an unstable intermediate was detected by NMR followed by extensive decomposition at room temperature, and a stannole was not observed. Vol. 24, Nr. 9, 2001New germoles with methoxy groups in 2,5-positions Germoles can be obtained in the same way as stannoles by 1,1-organoboration of di(l-alkynyl)-germanium compounds (Scheme 2) [9]. In general, the 1-alkynylgermanium compounds are less reactive towards EtjB when compared with their tin analogues. However, most of the 1-alkynylgermanium derivatives react with Et3B at room temperature or after gentle heating at 50 to 70°C. We have prepared di(lmethoxyethynyl)dimethylgermanium, Me 2 Ge(C*C-OMe) 2 which proved fairly stable towards thermally induced decomposition. These properties enabled us to carry out 1,1-organoboration reactions, leading straightforwardly to new germoles 14 and 15 (Scheme 7) [18]. This particular pattern of substituents, with methoxy groups in 2,5 and a boryl group in 3-position is now available for the first time. According to "B NMR spectra, coordinative 0-»B interactions are negligible. The new germoles undergo [4+2] cycloadditions with dimethyl acetylene dicarboxylate in the usual way [19]: the 7-germa-noibornadiene derivatives 16 and 17 were detected by NMR in solution before they rearrange into the respective benzenes 18 and 19 by ejection of dimethylgermylene which forms a polymer. In contrast, the analogous stannoles were not accessible from the reaction of Me 2 Sn(C"C-OMe)2 [20] with Et3B. Although a zwitterionic intermediate as shown in Scheme 2 could be detected by NMR spectroscopy at -40 °C, decomposition into numerous products occurred when the mixtures were allowed to reach ambient temperature.
Within the frame of a project on biologically active organometallic compounds twenty five triorganotin and organogermanium carboxylates of the type R 3 M0C(0)CH(0X)Ph (M = Sn, Ge; R = Me, Et, n-Bu; X = H, Me, C(0)Me, C(0)CF 3 , R 3 Ge), several diorganotin carboxylates R 2 Sn[0C(0)CH(0X)Ph] 2 (R = Et, n-Bu; X = Me, C(0)Me and {[R 2 Sn0C(0)CH(0X)Ph] 2 0} 2 (R = Et, n-Bu; X = Me, C(O)Me) and a new type of triorganogermanium carboxylates R 3 GeC^CCH 2 0C(0)CH(0X)R' (R = Me, Et, R' = Ph, Me, X = COCH 3 , COCF 3 ) have been synthesized and characterized by elemental analysis and structural methods (NMR, X-Ray, IR and Mössbauer). Introduction.Organotin and organogermanium compounds are the subject of special interest as potential antitumor agents. The literature analysis shows that antitumor activity is mostly characteristic of the covalent compounds of germanium and tin, in which the fragments forming the intra-and intermolecular coordination bonds with germanium and tin atoms do exist.The organotin and organogermanium carboxylates are of this type. The new organogermanium and organotin derivatives of α-substituted phenylacetic acids are described in this paper. Because of the specific properties of organotin and organogermanium carboxylates we will first describe the germanium compounds, and, afterwards, the derivatives of tin.
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Hydroxamic acids as the precursors of their organogermanium and organotin derivatives have been themselves intensively studied fi'om the viewpoint of their potential biological activities [1-3]. The wide spectrum of biological activities, from fungicide, bactericide and antiflammatory to psychotropic and antitumor, has been demonstrated for various organic derivatives of hydroxamic acids. Mironov and coworkers [4] at first obtained the C-germylated hydroxamic acids with about 70% yield by the reaction of the methyl ester of 3-trimethylgermylpropionic acid with hydroxylamine chlorohydrate: 0C Me3GeCH2CH2COOCH3 + NH2OH HC1 Me3GeCH2CH2CONHOH HC1 KOH Me 3GeC H2CH2CONHOH They have expanded later [5,6] this method to obtain some other 13-germylated hydroxamic acids: R 3 GeC H2C H(R')COOMe NH2OH, K OH R3G eCH2CH(R')CONHO K HCI, H20 R3G eCH2CH(R')CONHO H R3Ge Me3Ge, Et3Ge, I-AdMe2Ge; R H, Me The attempt to obtain o-germylacetohydroxamic acid was not successful, possibly due to the 13-elimination processes both in starting material and in final product: KOH
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