Allyltributyltin 2-chloro

Our first choice of alkene was allyltributyltin which had been previously studied by our group (see above). By employing the chloro(pyridine)cobaloxime(III)/magnesium redox couple in which chloro(pyridine)cobaloxime(III) was used in the catalytic amount, we were now able to synthesize the same allylated PCTFE (Eq. 4) with a higher degree of functionalization of approximately 50%. 

It should be noted that the similar addition did not succeed when a stoichiometric amount of chloro(pyridine)cobaloxime(III) was utilized. We found that the reaction of PCTFE did occur, but with a significant level of the side reaction (broad bands in 3100 -3700 and 1500 - 1800 cm-i regions in the IR spectrum. The rationale of the result was that a large number of PCTFE radicals were rapidly produced at one time. Some of these radicals were, therefore, available to react with THF concurrently with the desired addition to allyltributyltin. 

After the successful addition of PCTFE to allyltributyltin, the next alkene we examined was styrene. By treating PCTFE with styrene in the presence of magnesium and a catalytic amount of chloro(pyridine)cobaloxime(III), phenethylated PCTFE was obtained as depicted in Equation 5. 

Once again, it should be noted that the reductive condition in which the stoichiometric amount of chloro(pyridine)cobaloxime(III) was used, not only aided the addition of PCTFE to styrene, but also promoted the side reaction. In the IR spectrum of the resulting polymer, the reduction in the absorbance of the chloride band at 972 cm-i seemed to be too large, and the incorporation of oxygen in 3300 - 3600 cm-i region was also evident. The situation similar to the case of allyltributyltin might be applied in that THF possibly also took part in the reaction. 

In 1991, the syntheses of sialyl C-glycosides were introduced by Bednarski et ah, Paulsen et ah, and Vasella et al. Bednarski and Paulsen exploited a 2-halogeno derivative of Neu5Ac as a precursor of the anomeric radical, which was anticipated to be stabilized by the capto-dative effect of the C1 carboxylate group and ring oxygen. Bednarski reacted the 2-chloro derivative 195 with allyltributyltin and a catalytic amount of bis(tributyltin), and photolized for 18 h to obtain C-glycoside 196 as a 1/1 of anomeric mixture in 65% yield (O Scheme 53) [129]. 

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