Phenylcalcium iodide

There is still no efficient synthesis of 3-dibenzothiophenecarboxylic acid. The only recorded preparation is via metallation of dibenzothiophene with phenylcalcium iodide followed by carbonation, but the yield was poor. The successful use of 3-lithiodibenzothiophene to give the 3-aldehyde indicates that 3-bromodibenzothiophene would probably be the best precursor of the 3-acid. Both l,4,4a,9b-tetrahydrodibenzo-... 

Phenylcalcium iodide metallates dibenzothiophene in the 3-position however, it has no effect on the corresponding sulfone. Mercuration of dibenzothiophene has been accomplished by adding mercuric acetate to a melt of dibenzothiophene, but the position of mercuration was not established. Mercuric nitrate or bisulfite give no identifiable products. An unsuccessful attempt to metallate dibenzothiophene with cross-linked poly(p-lithiost5Tene) in ether has been recorded. ... 

Phenylcalcium iodide and pyridine give 2-phenylpyridine and either 2,5- (119) or 2,6-diphenylpyridine, depending on conditions.264 Scheme V was tentatively proposed to account for the results. Phenylation of 2-phenylpyridine by phenylcalcium iodide gave only the 2,6-isomer. As was appreciated by the authors,264 the replacement of a hydride ion at C-5 by a phenyl anion is a controversial stage and seems, at first sight, mechanistically improbable. If the nitrogen atom is assumed to form a relatively stable complex with the calcium atom,... 

Tschitschibabin reaction,290 thus counteracting the example based on 3-hydroxypyridine. The second reaction to be discussed is that of 2-picoline with sodamide at a relatively high temperature, when 3,6-diamino-2-picoline (126) is one of the products isolated.293 If this is so, this represents another example of the type of orientation recently observed in the phenylation of pyridine with phenylcalcium iodide which gave some 2,5-diphenylpyridine.264 Alternatively, a 3,4-pyridyne intermediate (125) might perhaps actually be involved here. The evolution of hydrogen is not mentioned in this case. The decarboxylation of pyridine carboxylic acids under strongly basic conditions is unexceptional. 

Scheme 9 Synthesis of the dimeric tmeda adduct of diphenylcalcium. After the (salt)metathesis reaction of phenylcalcium iodide with potassium tert-butoxide and addition of tmeda dinuclear [(Ph)Ca(p-Ph)(tmeda)]2 can be isolated...

Scheme 14 Modification of phenylcalcium iodide including exchange of the iodide anion via salt metathesis reactions (top row) and exchange of the neutral thf coligands by other Lewis bases such as dme, 18-crown-6, and tmeda (bottom row)...

Scheme 15 H and NMR parameters of phenylcalcium iodide in [DgJTHF. The C NMR increments are listed in comparison to benzene...

Table 2 summarizes observed and calculated NMR shifts of a variety of substituted phenylcalcium iodides in THF. Although the additivity of such empirical increments is an oversimplification, neglecting steric and electronic substituent interactions, the calculated values show acceptable deviations from the observed chemical shifts. Larger differences were observed for the ipso carbon of sterically crowded derivatives such as [(Mes)Cal(thf)4] [93] as well as for compounds where quinoid mesomeric forms might contribute to the overall structure like in case of [(p-Me2N-C6H4)Cal(thf)4] [84]. 

Scheme 16 Directed ortho-calciation (DOC) of 1,3-dimethoxybenzene with phenylcalcium iodide in THF yielding dinuclear [ 2,6-(MeO)2C6H3 3Ca2l(thf)3]...

Scheme 17 Proposed mechanism of the reaction of phenylcalcium iodide (coordinated thf ligands are omitted for clarity) with benzonitrile. In order to guarantee a low concentration of PhCN this substrate is generated in a preceding equilibrium of [ Ph-C(NSiMe3)2 K] with KN(SiMe3)2 and PhCN...

Langer J, Gorls H, Westerhausen M (2007) Phenylcalcium iodides with silyl substituents in para-position. Inorg Chem Commun 10 853-855... 

Fischer R, Gdrls H, Westerhausen M (2005) Reinvestigation of the synthesis of phenylcalcium iodide and the first structural characterization of a heavy Grignard reagent as [((thf>2CaPhI)3-(thf)CaO] with a central Ca4 tetrahedron. Inorg Chem Commnn 8 1159-1161... 

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