Organotin amides preparation

Aminations of alkyl halides and carboxylic esters are performed with organotin amides, which are also employed for the preparation of enamines (eq (118)) [113],... 

N-organotln ketenelmldes are only reported in the literature very recently. All derivatives known decompose on heating above 50°. In common with most organotin amides, hydrolysis with moist air is facile. The compounds summarized in Table 239 prepared by the following methods. 

The ester 870 is prepared by the cross-coupling of the chloroformate 869 with an organotin reagent. Some chloroformates are easily decomposed by a Pd catalyst, and hence the reaction should be carried out by slow addition of the chloroformates. Similarly, the amide 872 is prepared by the reaction of the carbamoyl chloride 871 [742]. The coupling of alkylcopper with ethyl chloroformate catalyzed by Pd affords esters[743]. 

Schreiber and co-workers (436) prepared a library calculated to contain 2.18 million polycyclic compounds through the 1,3-dipolar cycloaddition of a number of nitrones with alkenes supported on TentaGel S NH2 resin (Scheme 1.83). (—)-Shikimic acid was converted into the polymer bound epoxycyclohexenol carboxylic acid 376 (or its enantiomer), coupled to the resin via a photolabile linker developed by Geysen and co-workers (437) to allow release of the products from the resin in the presence of live cells by ultraviolet (UV)-irradiation. A range of iodoaromatic nitrones (377) was then reacted with the ot,p-unsaturation of the polymer-bound amide in the presence of an organotin catalyst, using the tandem esterification/ dipolar cycloaddition methodology developed by Tamura et al. (84,85) Simultaneous cyclization by PyBrop-mediated condensation of the acid with the alcohol... 

Tin-nitrogen bonded compounds are generally formed by reaction of an alkali or alkaline earth metal amide with an organotin halide compoundsofthe types R Sn(NR2)4- , ( = 1-3), (R3Sn) NR (n = 1-3), andcyc/o-(R2SnNR0 ( = 2 or 3) can be prepared (equation 79). Other routes include transaminations (equations 80 and 81). Tin carboxamides and snlfonamides have been obtained by reaction of tin oxides or hydroxides with amides (equation 82). 

Organotin esters of the oxy- and thio-acids of phosphorus can be prepared inter alia by azeotropic dehydration of a mixture of the organotin hydroxide or oxide and the acid, or by treating a tin alkoxide or tin amide with the acids, or an organotin halide with a salt of the phosphorus acid. By using different molecular ratios of the reactants, products of different compositions can be obtained. Attempts to prepare phosphites may result in an Arbuzov rearrangement to a phosphorus(V) compound (e.g. equation 13-11).47... 

Organotin alkoxides and phenoxides can be prepared from the reaction of an alkali metal alkoxide or phenoxide with the appropriate organotin halide. Triorganotin alkoxides and phenoxides are available from the reaction of bis(triorganotin) oxides with alcohols or phenols or the corresponding carbonates, and the amides R Sn(NR"2)4 react with alcohols to give the corresponding alkoxides. 

Borane is an effective reducing agent for organotin alkoxides and amides,11 and this has been exploited in the preparation of diorganotin dihydrides from the dioxastan-nolanes which can readily be obtained by azeotropic dehydration of a mixture of diorganotin oxide and 1,2-diol (e.g. equation 15-9).12... 

Amidostannanes containing the groups Sn-NC(=0)R or Sn-NS(0)2R are easier to prepare and to handle than are the aminostannanes. The acidity of the proton on nitrogen in the parent amide is now sufficient for reaction to occur with organotin hydroxides, oxides, and alkoxides (and aminotin compounds), and, once formed, the amidostannanes are less sensitive to moisture. A variety of amidostannanes is also available from the addition of Sn-0 and Sn-N bonded compounds to nitrogen heterocumulenes. 

The organotin thiolates (mercaptides) are usually prepared by substitution by a sulfur nucleophile at a tin centre. Suitable pairs of reactants are (1) thiol and tin oxide, alkox-ide, or amide, (2) thiol and tin halide in the presence of a base such as sodium hydroxide, sodium carbonate, ammonia, or triethylamine, or (3) metal thiolate and tin halide. Examples are shown in equations 17-20,33 17-21,33 and 17-22,34 and some of the common products are listed in Table 17-2. 

Various organotin compounds with tin-heteroatom bonds are synthesized by the reactions of halostannanes with the corresponding heteroatom nucleophiles. For example, trialkyltin alkoxides and trialkyltin amides are prepared by the treatments of halostannanes with sodium alkoxides (eq (139)) [134] and lithium amides (eq (140)) [135], respectively. Tin alkoxides are also formed by the reaction of alcohols with tin amides (eq (141)) [136]. 

The N-organotin derivatives listed here include also two compounds derived from the isomeric imidoester form of the amide. The compounds summarized in Table 2 0 are prepared by methods from the following scheme. 

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