Trialkyltin salts

The point of attack of trialkyltin salts (RaSn" ), which are highly active fungicides, is believed to lie in the oxidative phosphorylation of mitochondria (Aldridge, 1958). The tributyl homologue is the most used because it is the least toxic for mammals. 

Reactions of highly electron-rich organometalate salts (organocuprates, orga-noborates, Grignard reagents, etc.) and metal hydrides (trialkyltin hydride, triethylsilane, borohydrides, etc.) with cyano-substituted olefins, enones, ketones, carbocations, pyridinium cations, etc. are conventionally formulated as nucleophilic addition reactions. We illustrate the utility of donor/acceptor association and electron-transfer below. 

A trialkyl- or triarylstannyl group can also be added to an aromatic ring. One way this can be accomplished is by treating an aromatic or heteroaromatic compound possessing an active hydrogen(s) with an alkyl lithium and then reacting the lithium salt with a trialkyltin halide (equation 97). Another general method that has been used to attach a trialkyl- or... 

These observations do not, however, mean that TBT carboxylates and TBTCl are ionic in nature. After detailed analysis of the physical evidence such as the low specific conductance and dipole moment of trialkyltin halides, Neumann has concluded that they have no "salt-like constitution" (6). Bonding in the trialkyltin carboxylates also is essentially similar to that in covalent alkyl esters, as evidenced by the low dipole moment of 2.2D for tributyltin acetate in benzene, as compared to 1.9D for alkyl acetates (7). 

The lithium salts of acyclic secondary amines 92 can be conveniently transformed into the corresponding carbamoyllithiums 89 at —78 °C. Under these reaction conditions they react with trialkyltin chlorides to give carbamoyl stannanes 93 (Scheme 24)98. In the case of benzyl and allyl halides, an alkylation can occur affording products 94. However, when trialkylsilyl chlorides were used as electrophiles no carbamoyl silanes could be detected.. V-Alkyl thiocarbamates 95 can be prepared by reaction of the same intermediates 89 with sulfur followed by. S -alkylation at 0°C (Scheme 24)". 

Alkyl and aryltin(IV) diphenyldithioarsenates R Sn(S2AsPh2)4 ( = 2, R = Me, Bu , Ph = 3, R = Me, cy, Ph) are available from the organotin halides and the sodium salt of diphenyldithioarsenates. The dialkyl and trialkyltin species are four-coordinate by spectroscopy whereas the phenyl derivatives are six-coordinate. A structural study of Me2Sn(S2AsMc2)2 reveals a four-coordinate tin center with monodentate coordination of the dithioarsenate." ... 

Several new procedures for the selective oxidation of secondary alcohols in the presence of primary alcohols have appeared. Distannoxane-bromine, a neutral reagent, efficiently oxidizes secondary or benzylic alcohols to ketones in the presence of primary alochols.62 Trialkyltin alkoxides and bromine oxidize both primary and secondary alcohols.63 Woelm W-200, neutral, dehydrated alumina oxidizes secondary alcohols to ketones in the presence of primary alcohols with trichloroacetaldehyde as the hydride acceptor.6 The reverse reduction process had previously been reported. Oxidation of triphenylmethyl ethers of primary, secondary diols with triphenyl carbenium salts proceeds only at the secondary positions.65... 

An alternative procedure for reductive decarboxylation without the use of trialkyltin hydrides as hydrogen atom donors has been developed Alkane carboxylic acid esters derived from AT-hydroxypyridine-2-thione decomposed to alkyl radical, which can readily accept a hydrogen atom from t-BuSH (equation 74) to give alkanes. This reaction can be conveniently performed as a one-pot experiment wherein the acid chloride of an alkane carboxylic acid, the sodium salt of thiohydroxamic acid, t-BuSH and 4-dimethyl-aminopyridine (DMAP) in benzene solution are heated to reflux. This procedure works well for COOH groups attached to primary and secondary carbon atoms. Instead of AT-hydroxypyridine-2-thione, one can use other thiohydroxamic acids, viz. iV-hydroxy-AT-methylthiobenzamide, 3-hydroxy-4-methylthiazole-2(3if)-thione (equation 75) and l-iV-hydroxy-3-AT-methylbenzoylenethiourea for decarboxylation reactions. 

In complexes with antibiotics [amoxicillin, ampicillin, methiciUin, penicilUnG, cephalexin and ciprofloxacin (Figure 12.16, a-c)], polymeric compounds may be originated by direct reaction between dialkyltin(IV) chlorides and antibiotic sodium salt, or by direct reaction between trialkyltin(IV) hydroxides and free antibiotic acid. Other combinations (diorganotin oxide/free acid ligand triorganotin(IV) chloride/antibiotic salt) produce monomeric species. 

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