Trimethylstannyl ethers —

The crude product is dissolved in petroleum ether (10 mL) (Note 13) and poured onto a column (45-mm diameter) filled with 350 g of silica gel (Merck 230-400 mesh) for flash chromatography. Elution under pressure (Note 14), initially with 2% diethyl ether in petroleum ether (Note 15) and then with increasing amounts of diethyl ether (up to 10%) in petroleum ether, gives, after removal of the solvent under reduced pressure, l-trimethylstannyl-3,3-dimethoxypropane as a colorless liquid (11.9 g 81%). 

An nice example of the formation of a five membered ring in crosscoupling reaction is the hexamethyldistannane mediated ring closure of the dihalogenated diaryl ether shown in 3.1. The first step of the process is the palladium catalyzed exchange of one of the iodides to a trimethylstannyl moiety, followed by the closure of the five membered ring in Stille coupling. 

An alkyl group (primary, secondary, or tertiary) can be added to the oxime ether CHr=NOCH2Ph by treatment with the appropriate alkyl halide and an equimolar amount of bis(trimethylstannyl)benzopicolinate.483 This reaction, which is a free radical addition, is another way to extend a chain by one carbon. 

To a solution of the trimethylstannyl compounds (1 mmol) in methanol (20 mL, 0.05 M) is added ceric ammonium nitrate (10 mmol, commercial grade) at 25°C, and the solution is stirred until the aldehyde has been converted to dimethyl acetal (10 h). The reaction mixture is poured into ether, washed three times with water, dried (MgS04), and concen-... 

Dilithium(trimethylstannyl) 2-thienyl)cyanocuprate, (CH3)3SnCu(2-Th)CNLi2 (l)17. The cuprate is prepared by addition of CH3Li (2 equiv.) in ether to a THF solution of [(CH3)3Sn]2 (1 equiv.) and thiophene (1 equiv.) the reagent is formed after addition of CuCN (1 equiv.). 

Exchange reaction can also be carried out by treating bis(trimethylstannyl) sulfide (79) with the a-mercurated ketone (80) to yield the enol stannyl ether (81) and its C-isomer7 Direct reaction of carbonyl compounds with trialkylstannylamines can also give enol stannyl ethers. An example is the preparation of compound (82 Scheme 27). °... 

Pyridines (and quinolines) bearing a trimethylstannyl (SnMes) substituent at the 2-, 3-, or 4-position undergo iododemetallation to give the corresponding iodo-derivatives upon treatment with iodine. The trimethylstannyl compounds are themselves prepared by the reaction of the corresponding chloro-or bromo-derivatives with trimethylstannylsodium. The selective 3-debro-mination of 3,5-dibromo-4-hydroxy-2-pyridone has been reported. The reaction of 3-chloro-4-cyanopyridine with methanolic sodium methoxide gives the imino-ether (24) whereas treatment with sodium methoxide in DMF... 

FormyMestannylation. A trimethylstannyl group attached to an aromatic ring or an alkenyl position is liable to replacement on reaction with dichloromethyl methyl ether. Aldehydes are formed. 

Sila-WUtigrearrangements. The Si-lithio derivatives of W-silyl allylamines undergo rearrangement on addition of 12-crown-4 at -45°. The lithio species are made from the corresponding trimethylstannyl compounds by treatment with r-BuLi. A similar reaction is possible in the oxygen- (not N-) based systems, but the 5i-lithiosilyl allyl ethers can be formed only by transmetallation from tertiary allyl ethers. 

The protection of an a, p-unsaturated ketone by a conjugate addition strategy is the subject of our last example but it does not involve the use of an 0,0-acetal. During a synthesis of the cockroach pheromone Periplanone B. Still needed to perform a copper(I)-mediated Sn2 reaction on the allylic acetate 37.1 [Scheme 2.37], In order to prevent competing addition to the a, p-unsaturated ketone, it was protected temporarily by conjugate addition of trimethylstannyl-lithium and trapping of the intermediate enolate with chlorotrimethylsilane. The desired Sn2 reaction was then performed on the adduct 37.2 and the a.p-un-saturated ketone recovered by oxidation of the C-Sn bond to a C-OH using m-chloroperbenzoic acid. Concomitant destruction of the labile enol ether and -elimination of water returned the a, p-unsaturated ketone 373. 

Chemistry. A new method has been described for the regio- and stereo-controlled polyprenylation of quinones by means of trimethyltin derivatives. The polyprenyl trimethylstannanes (200) were prepared from the polyprenyl halides (201) and trimethylstannyl-lithium, and were then coupled with the required benzo-quinone (202) or naphthoquinone (203) in the presence of BFs-ether to give a quinol which was reduced with Ag20 to the ubiquinone (204) or vitamin K... 

Oligothiophenes end-capped with polybenzyl ether dendrons were prepared by Frechet s group (Scheme 1.70) [508]. Benzyl ester-substituted quinquethiophene 5.65 was deprotected in basic medium to the carboxylic acid and converted to the corresponding acid chloride using oxalyl chloride. This was then connected to a G5-hydroxyl-terminated Frdchet dendron by ester linkages. Stille-type coupling of the terminally brominated quinquethiophene and 2,5-bis(trimethylstannyl)thiophene afforded the highly... 

Reagents and conditions (i) KOH, THF/H2O. (ii) Oxalyl chloride, THF. (iii) OFI-polybenzyl ether dendron, K2CO3 18-crown-6. (iv) 2,5-Bis(trimethylstannyl)thiophene, Pd(PPh3)2Cl2, DMF. 

In a similar manner, the reaction of cyanuric fluoride 55 with tris(trimethylstannyl) amine in dry ether at 0 °C leads to the formation of 2,4-difluoro-6-[di(trimethylstannyl)]-amino-l,3,5-triazine 131 (Scheme 52) [5],... 

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