Desilylations sulfoxide

The reaction of the aldehyde 174, prepared from D-glucose diethyl dithio-acetal by way of compounds 172 and 173, with lithium dimethyl methyl-phosphonate gave the adduct 175. Conversion of 175 into compound 176, followed by oxidation with dimethyl sulfoxide-oxalyl chloride, provided diketone 177. Cyclization of 177 with ethyldiisopropylamine gave the enone 178, which furnished compounds 179 and 180 on sodium borohydride reduction. 0-Desilylation, catalytic hydrogenation, 0-debenzyIation, and acetylation converted 179 into the pentaacetate 93 and 5a-carba-a-L-ido-pyranose pentaacetate (181). 

SULFOXIDES Chlorotrimethylsilane- Zinc. Sodium borohydride-Cobalt(II) chloride. DESILYLATION Cesium fluoride. Potassium /-butoxide-Dimethyl sulfoxide. Potassium hydride. 

Numerous dioxetanes with varying atom (X) and protecting group (PG) have been synthesized over the last decade in order to study the CIEEL mechanism. The following serve as prototypical examples. The most prevalent trigger is that of a siloxyphenyl substituent such as that incorporated into dioxetane 54. Tetrabutylammonium fluoride (TBAF) is used in an aprotic solvent, such as dimethyl sulfoxide (DMSO) or acetonitrile, to desilylate to afford the unstable phenolate 55 (Scheme 11) <2002MI305>. 

Alkynic sulfoxides have been made from trimethylsilylethynyl-magnesium bromide and the resulting alkyne desilylated on silica gel(eq 7). ... 

Alternatively, oxidation of the sulfide to the sulfoxide followed by desilylation without allylic migration using CsF and sulfoxide pyrolysis gave 50, having the zygosporin G ring system in 63% yield. 

Our synthesis of homochiral acetylenic sulfoxides is outlined in Scheme 1. The Grignard reagent of trimethylsilyl acetylene was reacted with sulfinates 6a-c in toluene. After potassium fluoride desilylation, optically pure acetylenic sulfoxides ( )-(+)- were obtained in good yield (Scheme 1) [7,8]. 

Compound 89 was converted into 91 through epimerization at C5 of the ketone 90. The aldehyde 93 reacted with the lithium enolate of ethyl trityl ketone to give the desired aldol 94 as a sole product, which was converted into the (R)-sulfoxide 95 through the epimerization of the (S)-sulfoxide. The lithiated 95 was added to the ketone 91, followed by desulfurization and desilylation, to give the adduct 96. The seco-acid derived from 96 was cyclized by Corey s method followed by deprotection to give (9S)-9-dihydroerythronolide B, which was converted to erythronolide B (55) after 3,5-0-benzylidenation, oxidation and debenzylidenation. 

Recently, the fluoride ion-catalysed desilylation of p-tolyl l-(trimethylsilyl)vinyl sulfoxide (55) and reaction with aldehydes such as benzaldehyde (56) to give the corresponding allylic alcohol (57) has been studied (Scheme 5.18) [57]. The diastereoselectivity of the reaction was not evaluated and the products were obtained in moderate to good yields. The authors suggested possible mechanistic pathways for the reaction. 

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