INTRA-ANNULAR REACTIONS OF THE (1,3-XYLYLENE)-18-CROWN-5 SYSTEM - SYNTHESIS AND CRYSTAL-STRUCTURE OF [2(BROMOMAGNESIO)-1,3-XYLYLENE]-18-CROWN-5, [2(BROMOMERCURIO)-1,3-XYLYLENE]-18-CROWN-5 AND BIS[(L,3-XYLYLENE-18-CROWN-5)-2-YL]MERCURY

The Grignard compound [2-(bromomagnesio)-1,3-xylylene]-18-crown-5 (4) was prepared from the aryllithium compound (2-lithio-1,3-xylylene)-18- crown-5 (9) and magnesium bromide. The crystal structure of 4 shows th at it crystallizes without solvent and is coordinatively saturated (di storted octahedral) by complexation of the magnesium with four of the five crown ether oxygens. The 1:1 reaction of 9 with HgBr2 yielded the corresponding organomercury compound [2-(bromomercurio)-1,3-xylylene] -18-crown-5 (10), which crystallizes without solvent. Its crystal stru cture reveals that intramolecular Hg-O coordination occurs with two of the five oxygens, and only weak interaction with a third crown ether oxygen. Reaction of 10 with metallic magnesium lead to the symmetric c ompound bis[(1,3-xylylene-18-crown-5)-2-yl]mercury (11). The centrosym metric crystal structure of 11 shows that the mercury is intramolecula rly coordinated with only four of the ten oxygens; the mercury atom is completely shielded by the crown ether rings. This shielding is proba bly the reason for the failure to bring about reaction of 11 with magn esium to give the corresponding diarylmagnesium compound. The crown et her Grignard 4 was treated with deuterium oxide, chlorotrimethylstanna ne, iodine and benzophenone to give the products (2-D-1,3-xylylene)-18 -crown-5 (14a), (2-trimethylstannyl-1,3-xylylene)-18-crown-5) (15), (2 -iodo-1,3-xylylene)-18-crown-5 (16) and 2-(diphenylhydroxy)methyl-1,3- xylylene)-18-crown-5 (17) (the latter being converted into its methyl ether 1,1-diphenyl-2-oxapropyl)-1,3-xylylene)-18-crown-5 (17a) for ide ntification), respectively. The lithium compound 9 was treated with be nzophenone, chlorotrimethylgermane, chlorodiphenyrphosphine and 4,4'-d imethoxybenzophenone to give intra-annularly substituted crown ether d erivatives 17, (2-trimethylgermyl-1,3-xylylene)-18-crown-5 (18), (2-di phenylphosphinyl-1,3-xylylene)-18-crown-5 (19) (the latter undergoing slow oxidation to (2-oxodiphenylphosphinyl-1,3-xylylene)-18-crown-5 (2 0)) and xy-diphenylhydroxymethyl)-1,3-xylylene)-18-crown-5 (21) (which was converted under acidic conditions to '-cyclohexylidene)methyl]-1, 3-xylylene)-18-crown-5 (22)), respectively.