Tributyltin carbamate

Crich and Rumthao reported a new synthesis of carbazomycin B using a benzeneselenol-catalyzed, stannane-mediated addition of an aryl radical to the functionalized iodocarbamate 835, followed by cyclization and dehydrogenative aromatization (622). The iodocarbamate 835 required for the key radical reaction was obtained from the nitrophenol 784 (609) (see Scheme 5.85). lodination of 784, followed by acetylation, afforded 3,4-dimethyl-6-iodo-2-methoxy-5-nitrophenyl acetate 834. Reduction of 834 with iron and ferric chloride in acetic acid, followed by reaction with methyl chloroformate, led to the iodocarbamate 835. Reaction of 835 and diphenyl diselenide in refluxing benzene with tributyltin hydride and azobisisobutyronitrile (AIBN) gave the adduct 836 in 40% yield, along with 8% of the recovered substrate and 12% of the deiodinated carbamate 837. Treatment of 836 with phenylselenenyl bromide in dichloromethane afforded the phenylselenenyltetrahydrocarbazole 838. Oxidative... 

The insertion reaction of heterocumulenes can be used to syuthesize carbodiimides having two different substituents. For example, the carbamate 157 derived from an isocyanate and bis(tributyltin)oxide can be reacted with an isothiocyanate to give a carbodiimide 158 with substituents derived from the isocyanate and the isothiocyanate. ... 

When deprotection reactions of the Aloe group with a palladium catalyst and pseudometallic hydrides, namely tributyltin hydride, sodium borohydride, or phenylsUane, are performed in the presence of an acylating agent, the deprotected amino group is directly obtained in its acylated form.P This tandem deprotection-acylation reaction is believed to involve a concerted decarboxylative condensation of the initially formed pseudometallic carbamate with the acylating agent, as represented in Scheme 8 in the case of hydrostannolysis.t ... 

Human natural killer (NK) lymphocytes are vital to immune system defense against viral infection. They are also crucial in protecting against primary tumor formation. In vitro exposures to low levels of two organotin pesticides, tributyltin (4.76) and triphenyltin (4.19), and two carbamate pesticides, maneb (0.62) and ziram (1.23), produced significant loss of cytotoxic function of NK cells after 6 days of exposure. The toxicities of the pesticides also increased very significantly with exposure durations J51 It should be noted that exposure to ziram can come from other sources. It is used as an additive in rubber products such as latex gloves. 

Other carbamates in which the O-alkyl bond can be easily cleaved can serve as amino-protecting groups. Allyloxycarbonyl groups are cleaved by a combination of tributyltin hydride and a Pd(II) catalyst." This reaction involves liberation of the carbamic acid by oxidative addition to the palladium. The allylpalladium species is then reductively cleaved by the stannane. 

Most functional group conversions abxmdantly used on carbohydrate derivatives are also compatible with thioglycosides, e.g. SN2-displacements of sulfonates [37], azo transfer [38], and deoxygenation by tributyltin hydride reduction of o-carbonyl carbamates [39]. During oxidations care has to be taken so not to obtain the sulfoxide derivative (if that is not desired). DMSO and also PDC-mediated oxidations can usually be performed without problems [40]. 

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