Hydroxy stannylation

In comparison to other vinylic compounds , the vinyl proton in 1-alkenyl carbamates, deprotonation has a very high kinetic acidity . After protection of the 4-hydroxy group in the homoaldol products by silylation, deprotonation (w-BuLi, TMEDA, diethyl ether or THF) of enol carbamate 384 is complete at —78 °C (equation 103), and the resulting vinyUithium 385 can be kept at this temperature without decomposition for several hours. Stannylation , silylation , methoxycarbonylation (with methyl chloroformate) ... 

In a similar manner, intramolecular cyclization of the O-stannyl ketyl derivatives 201 and 206, generated from the oxazolyl aldehydes 200 and 205, provides a facile method for the chiral synthesis of 3-hydroxy-2-(hydroxymethyl)-5-substimted-pyrrolidines 202 and 203 and the piperidine analogues 207 and 208 that can be successfully transformed into naturally occurring amino alcohols, (+)-bulgecinine 204 and (—)-desoxoprosopinine 209, respectively (Fig. 

S-hydroxy-2-alkenoate ester 4-stannyl-2-alkenoate ester 1761... 

Then the other hydroxy groups are benzylated. If (Bu3Sn)20 and BnBr are used for benzylation the 4-OH unprotected sugar 45 is formed, because of a stannyl complex which acts as in the case of 39. 

The reaction of hydroxy tellurium pentafluoride with chlorotrimethylsilane, chlorotrimeth-ylstannane, or tetramethylstannane produced trimethylsilyl(stannyl)oxy tellurium pentafluoride2. 

Propanol 3-(Chlor-dibutyl-stannyl)-E19a, 894 (En-ol + R2SnH2) Zinn Bis-[2-methyl-propylj-(3-hydroxy-propyl)- -chlorid XIII/6, 283... 

Diketene similarly reacts readily with tributyltin oxide in THF at room temperature47 to give the stannyl 3-stannyloxybut-3-enoate which rearranges to the 2-enolate this enolate will then give an ene reaction with an aldehyde,48 or react with an alkyl halide,49 followed by decarboxylation, providing a route to ketones, enones, and ketoaldehydes. Similar reactions with bromomethyl P- or y-lactones result in the formation of P-hydroxy-y-lactones or y-hydroxy-5-lactones. 

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