Benzylic deoxygenative allylation

Allylation. Deoxygenative allylation of allylic and benzylic alcohols with allyItrimethylsilane is promoted by (FS02),NH. 

Reductions. The InCIj-Bu SnH/PhjP combination (catalytic in indium) reduces acid chlorides to aldehydes." Aryl ketones and secondary benzyl alcohols are deoxygenated with hydrosilanes using InCl, as cataly.st." Deoxygenative allylation of aryl ketones occurs when allyltrimethylsilane is added. ... 

Direct Deoxygenative Allylation of Substituted Benzylic Alcohols... 

Reaction with Allylic Halides, Alcohols, and their Derivatives. Allylation of allyl and propargyl trimethylsilyl ethers as well as benzyl and propargylic alcohol derivatives proceeds in the presence of a catalytic amount of Lewis acids, such as ZnC, TMS(OTf), and B(C6F5)3. Direct substitutions of the hydroxyl group of allylic, ben-zylic, and propargylic alcohols are catalyzed by HN(S02F)2, a rhenium-oxo complex, and InCls (eq 27). A combination of chlorodimethylsilane and allyltrimethylsilane effectively promotes the deoxygenative allylation of aromatic ketones in the presence of a catalytic amount of an indium compound, such as indium trihalide or metallic indium (eq 28). Allylation of cyclic allylic acetates with allyltrimethylsilane can be catalyzed by molecular iodine. ... 

The next step was reduction of the ester and O-benzyl ether groups in 6 with lithium in liquid ammonia. Note how the allylic alcohol survived these reduction conditions. Sometimes, allylic deoxygenation can... 

Allyl alcohols are deoxygenated under the same conditions used to break a benzyl oxygen bond. Over a palladium catalyst, loss of oxygen occurs along with double bond saturation. The presence of acids promotes hydrogenolysis. With platinum, nickel, or rhodium catalysts in neutral medium, progressively less oxygen... 

Dehydroproline, 157-158 Dehydrotosylation, 234 Demethylation, 30—31, 115, 204 Deoxygenation, 148 Deoxygenation of allylic and benzylic... 

Deoxygenation of aUyBc and benzyUc alcohols. Allylic and benzylic alcohols are conveniently reduced to the corresponding hydrocarbons in two steps. The alcohol is first converted into a pyridinium alkyl sulfate by reaction with sulfur trioxide-pyridine in THF at 0-3° (3-20 hours). Then lithium aluminum hydride (or LiAIH -AlClj, 3 1) in THF is added and the mixture stirred for I hour at 0° and then at 25° for 3-5 hours. Yields are high. In the case of allylic alcohols... 

Organolithiums. Allylic and benzylic alcohols undergo deoxygenative lithiation by treatment of their lithium alkoxides or phenyldimethylsilyl ethers with LDTBB. Alkyl phenyl selenides are also cleaved to give organolithium species that can react with aldehydes and allyl bromide. Some special alkyllithiums have been prepared from (2-pyridylthio)alkanes, which are available from carboxylic acids. ... 

De-N-protectionJ A-Allyl and A-benzyl derivatives undergo dealkylation on heating with TiClj-Li in THF under argon. The application of this method to the deoxygenation of aryl ketones via reductive amination with aniline is too elaborate (taking three steps) to be of any synthetic significance. 

Allylic and benzylic alcohols, ethers, aldehydes, ketones, and carboxylic acids are deoxygenated by an excess of lithium aluminium hydride in THF with catalytic quantities of CpaTiClj (e.g. Scheme 19). However, if the allylic double... 

The titanium-mediated deoxygenation step has also been made more general. For example, allylic and benzylic 1,4-diols and 1,4-dimethyl ethers are transformed into more highly unsaturated products under McMurry conditions. ... 

In the presence of Znl2, dichloromethane or dimethoxyethane solutions of NaBH3CN have been found to deoxygenate aryl aldehydes and ketones as weU as benzylic, allylic and tertiary alcohols in moderate to good yields. In spite of the unfavorably large excess of the reagent, the procedure is simple and the substrates require no previous transformations to halides or tosylates, so that the reagent can also be recommended for the synthesis of... 

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