Oxidative destannylation

Tandem addition of trimethyltin followed by cyclization in a 1,6-heptadiene system [Eq, (7)] proceeds with surprising efficiency [30]. Oxidative destannylation of the primary product gives a synthetically useful dimethyl acetal. An acetylene-terminated tandem addition is shown in Eq. (8) [31]. 

Acyliminium ions. Oxidative destannylation of A/-(a-stannylalkyl) amides leads to reactive electrophiles, which can react with enol silyl ethers, allylsilanes, allylstannanes, and trimethylsilyl cyanide. The stannyl group lowers the oxidation potential of the amidic nitrogen, without which the acyliminium ions do not form under the oxidation conditions. 

Oxidative Destannylation of j8-Stannylsilylenol Ethers. m-CPBA was used as the reagent of choice to functionalize the [3+4] annulation product of ketone enolates with /3-stannylacryloylsilanes leading to enediones (eq 28)7 ... 

Hanessian, S. and Ninkovic, S. (1996) Stereoselective synthesis of ( )-a-kainic acid and (-l-)-a-allokainic acid via trimethylstannyl-mediated radical carbocyclization and oxidative destannylation. /. Otg. Chem., 61, 5418-5424. 

S-Lactones. Oxidative cyclization of 3-hydroxy-5-tributylstannylpentanoic acids with Pb(OAc)4 results in destannylation and lactone formation. a-Substituted 8-lactones are obtained when alkanols undergo oxidation under CO (20 examples, 32-15%) ... 

An early contribution to use of the transition-metal-catalyzed pyridine formation reaction was the synthesis of vitamin Be (124) via the crossed-cyclotrimerization reaction of the bis-stannylated diyne 122 with acetonitrile under cobalt catalysis (Scheme 7.26) [36a andb]. The underlying crossed [2 - - 2 - - 2] cycloaddition reaction here provided the fused pyridine 123 in 76% yield after a regioselective destannylation effected by treatment of the cycloaddition product with aluminum oxide. 

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