Aryl lead compounds

Finally, reaction of the aryl lead compound 356, which was prepared from 355 by tin-lead exchange, with 357 led to the production of 358 in good yield (Scheme 34) (169). 

Arylboronic and arylborinic acids have been produced from the hydrolysis of intermediates in the reactions of aryl-tin and aryl-lead compounds with diborane. The preparation of di[bis(trimethylsilyl)methyl]chloroborane from the reaction of bis(trimethylsilyl)methyl-lithium and boron trichloride has been published. A new reagent for O-ethylboranediylation, ethylbis-(2-isopropyl-6-methyl-4-pyrimidinyloxy)borane (3) has been synthesized and used to prepare O-ethyl-boranediyl derivatives of alcohols, phenols, alkanediols, D-mannitol, and l-arabinose. Borane-methyl sulphide reportedly reacts smoothly with primary, secondary, and tertiary alcohols and phenols to provide a general and convenient synthesis of borate esters. ... 

It is the purpose of this chapter to summarize what is currently known about the stereochemistry and conformation of organogermanium, tin and lead compounds. Coverage is selective rather than exhaustive. The first section deals with compounds in which substitution by four different groups causes the metal atom to be stereogenic. We have limited our discussion to those cases in which at least three of the four substituents are alkyl or aryl. In this section we also briefly discuss pentacoordinated triorgano halostannanes. 

This class of rigid tricyclic fused oxazolidinones was synthesized in order to gain an understanding of the importance of the spatial relationship and torsional angle between the aryl and oxazolidinone rings with regard to antibacterial activity [51,65]. Considering the structure of an early lead compound,... 

Scheme 4. The compounds and intermediates on the rear plane of the bicubic system (farthest from the reader) are protonated on the pyridine nitrogen atom those on the front plane (nearest the reader) are not. Laviron s work has shown that the reduction of 14 and its corresponding N-oxide34, and indeed probably most aryl nitro compounds, proceeds by an ECEC sequence leading to the neutral N,N-dihydroxy [ArN(OH)2] intermediate at all proton concentrations from Ho = —6 to pH 9.6. This substance then loses water to form the nitroso compound, which then undergoes a second sequence leading to the arylhydroxylamine.

Plumbene-NHC complex 36 is generated by the reaction of an NHC with a bis(aryl)-lead(II) compound. The NHC-silylene adduct 37 also features a long C-Si bond with significant Si polarity. Pentacoordinated silicon(lV) and... 

This cyclization is a reaction developed by Mori, who carried out a series of investigations with tin reagent 33. Fluoride is a much more reactive anion for initiation than any of the other halides, although it often leads to decomposition of the starting materials. In the case of vinylic or aryl halogen compounds the iodides are easier to transform than the bromides, and chlorides are unrcactive. The carbonyl group can be derived from either an aldehyde or a ketone, and even esters are sufficiently electrophilic.22... 

The catalytic activation of aromatic C-H bonds leading to useful addition with new C-C bond formation is of considerable interest in organic synthesis and industrial processes, because it would provide simple and economical methods for producing aryl-substituted compounds directly from simple arenes, as shown in Scheme 1. 

Lead compounds with very large bulky groups such as Ph3PbOSiPh380 and [2,4,6-(MesSi CHCgPEkPbBr81 are monomeric due to steric shielding of the Pb atom by the bulky aryl substituents. 

As was mentioned in Section 1, the first synthesis of an organolead compound was reported by Lowig 210>211), who synthesized tetraethyllead by the reaction of a sodium-lead alloy with ethyl iodide. Some 35 years later, Polis 247,248) prepared the first aryl lead derivative by the reaction of bromobenzene with a sodium-lead alloy. Since 1923, the sodium-lead alloy-ethyl chloride reaction has been used for the commercial production of tetraethyllead. A similar reaction has also been used for the commercial production of tetramethyllead since 1960. The sodium-lead alloy-alkyl chloride reaction is discussed in Section 6. 

Because a number of these organometallic compounds are commercially available, they are convenient starting materials for the preparation of certain aliphatic and aromatic diorgano tellurium dihalides. Tetraorgano tin and lead compounds transfer only two of their four organic groups to tellurium. Experiments with dialkyl-diaryl compounds showed that only the aryl groups are transferred. 

Hexaphenyl dilead3, tetramethyl lead3, and triphenyl lead chloride4 donate phenyl groups to aryl tellurium trichlorides to produce aryl phenyl tellurium dichlorides in yields from 73 to 92%. The lead compounds are more reactive than the tin and silicon derivatives and even react at 20°. 

While it is difficult to ensure the rehable observation of the radical processes during the mixing of reagents, these are easily detected in the photoinduced reactions of aryl-substituted compounds of Ge and Sn. Laser pulse photolysis experiments show that direct photoionization of Ph3Ge(Sn) anion results in the neutral radical . The apphcation of the Chemically Induced Dynamic Electron Polarization (CIDEP) method has allowed the detection of polarized emission signal of the radicals, thus leading to a conclusion that direct photoionization of Ph3Ge(Sn) anion occurs from the triplet state (equation 7). ... 

Interaction of ferrocene and diazonium compounds, which is followed by loss of nitrogen, leads to a large number of derivatives 17, HI, 1, 14s, 30S) most of them, naturally, are aryl-substituted compounds. Ferrocene cannot only be mercuriated, but can also be metalled by lithium butyl or similar compounds such as sodium phenyl. A great variety of pt ibilities for substitution is afforded by the interaction of ferrocenyl lithium and halogen-containing compounds 5, 128, 143, 162). Carboxylic acids, in particular, may easily be obtained by formation of the lithium derivative of ferrocene and treatment with carbon dioxide. 

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