Subject organomercuries

Addition of several organomercury compounds (methyl, aryl, and benzyl) to conjugated dienes in the presence of Pd(II) salts generates the ir-allylpalladium complex 422, which is subjected to further transformations. A secondary amine reacts to give the tertiary allylic amine 423 in a modest yield along with diene 424 and reduced product 425[382,383]. Even the unconjugated diene 426 is converted into the 7r-allyllic palladium complex 427 by the reaction of PhHgCI via the elimination and reverse readdition of H—Pd—Cl[383]. 

Entry 5 is an example of the use of fra-(trimethylsilyl)silane as the chain carrier. Entries 6 to 11 show additions of radicals from organomercury reagents to substituted alkenes. In general, the stereochemistry of these reactions is determined by reactant conformation and steric approach control. In Entry 9, for example, addition is from the exo face of the norbornyl ring. Entry 12 is an example of addition of an acyl radical from a selenide. These reactions are subject to competition from decarbonylation, but the relatively slow decarbonylation of aroyl radicals (see Part A, Table 11.3) favors addition in this case. 

Cappon and Crispin-Smith [59] have described a method for the extraction, clean-up and gas chromatographic determination of alkyl and aryl mercury compounds in sediments. The organomercury compounds are converted to their chloroderivatives and solvent extracted. Inorganic mercury is then isolated as methylmercury upon reaction with tetramethyltin. The initial extract is subjected to a thiosulphate clean-up and the organomercury species are isolated as their bromoderivatives. Total mercury recovery was in the range 75-90% and down to lpg kg-1 of specific compounds can be determined. 

Ozonation was generally halted after all of the organomercurial had reacted. The resultant white solid was then collected, washed with CH2C12, dried, and subjected to analysis by powder x-ray diffraction with a Norelco analytical x-ray diffractometer. 

But the diazo method still had its grip on me. Which metals, apart from mercury, could be subjected to the method To answer this, many years were to pass because simultaneously I was working on other problems of interest to me. Eventually, the method of synthesis was extensively developed for aromatic derivatives of such elements as Hg, Tl, (Ge), Sn, (Pb), As, Sb, Bi. For the metals in parentheses the method was shown to just work, while for the others it is an excellent preparative procedure. In Table I the best versions are exemplified. At the same time, I and the first generation of my disciples, and also other scientists, applied the method to various organomercurials substituted at the aromatic nucleus (19-21), and to the naphthalene (22), triphenylmethane (23), and pyridine (24) series. 

The protic cleavage of the carbon-metal a-bond ranks among the simplest of all electrophilic substitution processes. As organomercurials are readily prepared in high purity, can be manipulated with ease and are monomeric in solution, most mechanistic studies of the protonolysis of carbon-metal o-bonds have focused on the protic cleavage of organomercurials. Reviews and a book have been published on this subject. 

Inorganic mercury was also isolated as methyl mercury upon reaction with tetra-methyl tin ° The initial extracts were subjected to thiosulfate clean-up, and mercury was isolated as the bromide derivative. The method yielded good agreement between gas-chromatographic and atomic absorption spectrometric data. Twenty-four samples were analyzed daily on a routine basis. Organomercurials could also be determined and the differences from inorganic mercury could be detected by these gas-chromatographic methods ... 

The use of TEMPO to effect oxidative demercuration was originally demonstrated by Whitesides [16], and is attractive because it gives a functional handle for further structural elaboration. This technique was invoked by Kang in the syntheses of (-t-)-lactacystin and (-l-)-furanomycin [17]. For example, alkene 10 was subjected to mercurioamidation conditions to afford the cyclized organomercury intermediate 11 (Scheme 4). Treatment with lithium borohydride in the presence of TEMPO forms the unstable organomercury hydride. This fragments to release the primary carbon radical, which is trapped by TEMPO to yield the masked alcohol product 12, an intermediate in the synthesis of the neurotropic factor (-l-)-lactacystin. 

Mercury is a soft metal and as such it is expected to form secondary bonds, most readily with sulfur, selenium, and other heavy non-metals. The situation is, however, more complex and secondary interactions with other electronegative atoms have also been observed in the solid state. Interatomic distances longer than the expected van der Waals distances are, moreover, sometimes observed between molecules orientated such that weak interactions lead to particular arrangements in the crystal [69]. The are numerous examples of secondary bonds in organomercury chemistry although most are intramolecular there are several examples of inter-molecular secondary bonds leading to supramolecular self assembly. A review has been published on this subject [70] and many new examples have subsequently been reported. 

Mixed-metal catalysts based on 002(00)9 have proved effective In the synthesis of N acyl amlnoaclds, starting with either allylic alcohols, oxiranes (eqn.15) or trifluoropropene. The oxidative carbonylatlon of organomercury compounds Is subject to solvent effects. The Pd catalysed carbonylative cross-coupling of aryl Iodides with triIsobutylaluminium gives secondary benzyl alcohols a variety of functional groups are tolerated.Carbamate esters... 

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