2,3-bis trimethylsiloxy

Moreover, the formation of enoxy-silanes via silylation of ketones127 by means of N-methyl-N-TMS-acetamide (1 72) in presence of sodium trimethylsilanolate (173) was reported in 1969 and since then, the use of silylating reagents in presence of a catalyst has found wide appreciation and growing utilization as shown in recent papers128-132 (Scheme 27). Diacetyl (181) can be converted by trifluoromethylsul-fonic acid-TMS-ester (182) into 2,3-bis(trimethylsiloxy)-l, 3-butadiene (7treatment with ethyl TMS acetate (7 5)/tetrakis(n-butyl)amine fluoride l-trimethylsiloxy-2-methyl-styrene (i<56)130. Cyclohexanone reacts with the combination dimethyl-TMS-amine (18 7)/p-toluenesulfonic acid to 1-trimethylsiloxy-l-cyclohexene (iSS)131. Similarly, acetylacetone plus phenyl-triethylsilyl-sulfide (189) afford 2-triethylsiloxy-2-pentene-4-one (790)132. ... 

This reaction offers some advantages over conventional methods as many acyloins can only be prepared by this method in good yields. Thus, by using ethyl acetate (289) in the first step 2,3-bis-(trimethylsiloxy)-2-butene (290) is obtained which can be easily hydrolysed to acetoin (310)19. Dicarboxylic acid esters undergo an intra-... 

Those bis(trimethylsiloxy)alkenes resulting in the first step are reactive intermediates which can be converted into a variety of compounds — they give an easy access to many products in a one pot synthesis. For instance via bromination of 3,4-bis(trimethylsiloxy)-3-hexene (303) 2,5-dibromo-3,4-hexadione (307) can be achieved199 whereas l,2-bis(trimethylsiloxy)stilbene (304) yieldsbenzil (308)i99 Simmons-Smith conditions were applied, too, and 2,3-bis(trimethylsiloxy)-2-butene (290) gives l,2-dimethyl-l,2-bis(trimethylsiloxy)cyclopropane (306)2OO ... 

Treatment of 2,3-di-ier/-butoxycyclopropenone with trifluoroacetic acid at 6 "C produced 2,3-dihydroxycyclopropenone (deltic acid, 4) in quantitative yield. This compound was also obtained by treatment of 2,3-bis(trimethylsiloxy)cyclopropenone with butanal at — 78 C in 98% yield. 

In contrast to metal enolates, enol silyl ethers are covalent compounds. It is easier to accommodate two or more enol silyl ether structures within the same molecule, whereas it would be more difficult to generate the corresponding enolate structures because of their strongly basic and reactive characters. 2,3-But-anedione has been converted to 2,3-bis(trimethylsiloxy)butadiene by a number of methods the best appears to be TMS triflate and EtiN in benzene. Likewise, 1,3-diketones have been converted to the... 

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