Enol ethers organotin

SlLYL ENOL ETHERS Chiorotrimethylsilane-Zinc, 82 Lithium amides, chiral, 159 Lithium tri-sec-butylborohydride, 167 Organotin reagents, 211 Osmium tetroxide-Trimethylamine N-ox-ide-Pyridine, 223... 

The stemona alkaloid stemonamide (49) was synthesized starting from a-stannyl acetate 47 and 2-stannyl pyrrolidine 48. The oxidative coupling of stannyl acetate 47 with acetylenic silyl enol ether affords the functionalized C-7 unit which corresponds to the side arm of the pyrrolidine ring. Then, introduction of the C-7 unit to the pyrrolidine ring is performed by the oxidative generation of acyliminium ion. The carbon skeleton of stemonamide was thus constructed efficiently as shown in Scheme 19 by employing organotin compounds. ... 

Hydroxyl protection. Enol ether 1 has been developed. A tetrahydropyranyl sulfoxide 2 is available for the formation of mixed acetals upon activation with Cp2ZrCl2-AgC104. The fluorous bromosilane 3 form siloxanes with improved acid stabilityA method for selective tosylation of diol systems that is known to be catalyzed by organotin oxides is also modifiable in terms of fluorinated catalysts. ... 

Sato and co-workers in 1991 showed the utilization of organotin triflate as the Lewis acid catalyst for the Michael addition step. Synthesis of octalone 30 is a good example in which silyl enol ether of cyclohexanone and MVK (1.3 1 ratio) reacts in DCM in the presence of 0.05 equivalent of Bu2Sn(OTf)2 at -78 C. After alkylation was complete, sodium methoxide in methanol was added, and the mixture was stirred at room temperature to give 30 in an excellent 89% yield. ... 

Addition of tributylstannyl-lithium to crotonaldehyde and protection of the resulting alcohol with chloromethyl methyl ether gives the stannane (192), which reacts with both alkyl and aryl aldehydes RCHO to form specifically the t/rr o-hydroxy-enol ethers (193). These latter compounds have been used to prepare tra/i5-4,5-disubstituted butyrolactones by hydrolysis and subsequent oxidation. Palladium-catalysed carbonylation of RX in the presence of organotin species constitutes a useful synthesis of unsymmetrical ketones, and in the example reported this year RX is an arenediazonium salt. The reaction, which is basically an aromatic acylation, proceeds in good to excellent yield. Another Pd-catalysed reaction of aromatics, this time aryl bromides, is their reaction with acetonyltributyltin (194), prepared from methoxytributyltin and isopropenyl acetate, to give the arylacetones (195). ... 

Organotin(IV) enol ethers 2.3.2.32 TinOn enol ethers... 

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