TBDMS allyl ether

NBS, CH3CN, H2O, 62-90% yield.The POM group has been selectively removed in the presence of an ethoxy ethyl ether, TBDMS ether, benzyl ether, p-methoxybenzyl ether, an acetate, and an allyl ether. Because the hydrolysis of a pentenyl 2-acetoxyglycoside was so much slower than a pentenyl 2-benzyloxyglycoside, the 2-benzyl derivative could be cleaved selectively in the presence of the 2-acetoxy derivative. The POM group is stable to 75% AcOH, but is cleaved by 5% HCl. 

PMB ethers can be cleaved oxidatively with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)11 in dichloromethane/water tor with cerium ammonium nitrate (CAN) in acetonitrile/water.12 Many other protecting groups such as esters, isopropylidene acetals, benzyl ethers, allyl ethers and f-butyldiphenyl silyl (TBDMS) ethers are stable to these conditions (Scheme 2.4). The cleavage reaction, with DDQ is initiated with a single-... 

Oxidation of a primary allylic alcohol over a secondary allylic alcohol has been achieved. Oxidation of the homoallylic alcohol of cholesterol by TPAP and NMO under ultrasonication conditions gives the dienone cholest-4-ene-3,6-dione in 80% yield. This oxidation was subsequently carried out in the presence of a labile TBDMS enol ether group which remained intact, while with both PCC and activated DMSO this protecting group did not survive. Oxidation of homopropargylic alcohols leads to allenones, as with other common oxidants. ... 

Allylic alcohols are versatile substrates for hydroformylation. Hydroformylation of allyl alcohol typically favors the linear regioisomer, and this reaction formed the basis of a route to manufacture 1,4-butanediol [15]. Landis recently reported the use of a chiral diazaphospholane for the asymmetric hydroformylation of aUyl silyl ethers [16]. The TBDMS aUyl ether, formed from reaction of allyl alcohol with TBDMSCl, was hydroformylated in 96%ee and 2 1 branched/linear to give the Roche aldehyde (12) which is a widely used chiral building block. High molar substrate/catalyst ratios (10,000 1) and low syngas pressures (15 psi) make this reaction potentially attractive for commercial development. 

Benzyl, allyl, methyl, THP, TBDMS, and TBDPS ethers are all stable to these conditions. A primary MEM group could be selectively removed in the presence of a hindered secondary MEM group. 

MeOH, reagent prepared by heating Bu2SnO and Bu3SnP04, heat 2 h, 90% yield." This method is effective for primary, secondary, tertiary, benzylic, and allylic THP derivatives. The MEM group and ketals are inert to this reagent, but TMS and TBDMS ethers are cleaved. 

DMSO, H2O, 90°, 79-87% yield. These conditions are only effective for primary allylic and homoallylic, primary benzylic, and aryl TBDMS ethers. ... 

I2, CH2CI2, 3A ms, 1-8 h, rt, 22-94% yield. The Bn, allyl, and TBDMS ethers are stable to these conditions, but TBS ether is partially cleaved. Phenolic prenyl ethers react to give chromanes. 

SnCLt, PhSH, CH2CI2, 78°C to 50°C, 5 min to 1 h, 88-93% yield. Benzyl, allyl, and TBDMS ethers are stable along with various esters. BF3-Et20 can also be used as a Lewis acid (83% yield). ... 

DDQ, CH3CN, H20. These conditions normally cleave the PMB group selectively in the presence of a TBDMS group,but in the case of an allylic derivative below the alcohol was oxidized directly to an aldehyde." This reaction has some generality in that other electron-rich substrates as well as a TES ether are similarly oxidized. It is also selective in that PMB ethers survive." It should be noted that in the presence of protic solvents, DDQ forms acidic adducts which are probably responsible for the hydrolysis. 

Photolysis at 254 nm, CH3OH, CH2CI2, phenanthrene, 51-84% yield. These conditions are selective for allylic and benzylic alcohols. In the absence of the phenanthrene, TBDMS ethers are also cleaved. ... 

Silyloxy allylic stannanes are isomerized with TBDMS triflate to (Z)--y-silyloxy allylic stannanes (eq 11). The resulting allylic stannanes undergo addition reactions with aldehydes in the presence of Boron Trifluoride Etherate to provide the 3-(r-butyldimethylsilyloxy)-4-hydroxyalkenes. ... 

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