Propargyl Alcohols and Their Derivatives

Catalytic Propargylic Alkylation of Propargylic Alcohols and their Derivatives 138... 

Synthesis.—Vinylidene adamantane (113) has been prepared and its reactions investigated.The synthesis of allenes from propargyl alcohols and their derivatives continues to provide a number of papers dealing with this extremely useful transformation. Ferric chloride catalyses the highly selective formation of allenes... 

For the last two decades, the use of the platinum- or rhodium-catalyzed intramolecular hydrosilylation/Tamao-Fleming oxidation sequence has been well recognized as a powerful method for the stereoselective synthesis of various structurally diverse alcohols (1,3-diols, 2-alkoxy-l,3-diols, and 2-aminoalcohols) and ketone derivatives (/3-hydroxyketones, y-hydroxyketones, o, /3-dihydroxyketones, and a,y-dihydroxyketones) from simple and readily available starting materials such as substituted allyl or propargyl alcohols and their homologues (4,177). Selected applications are presented in equations (24-26). 

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. ... 

In 1998 it was revealed that allenylidene-ruthenium complexes, arising simply from propargylic alcohols, were efficient precursors for alkene metathesis [12], This discovery first initiated a renaissance in allenylidene metal complexes as possible alkene metathesis precursors, then it was observed and demonstrated that allenylidene-ruthenium complexes rearranged into indenylidene-ruthenium intermediates that are actually the real catalyst precursors. The synthesis of indenylidene-metal complexes and their efficient use in alkene metathesis are now under development. The interest in finding a convenient source of easy to make alkene metathesis initiators is currently leading to investigation of other routes to initiators from propargylic derivatives. 

In parallel, since the first preparation of allenylidene-metal complexes in 1976, the formation of these carbon-rich complexes developed rapidly after the discovery, in 1982, that allenylidene-metal intermediates could be easily formed directly from terminal propargylic alcohols via vinylidene-metal intermediates. This decisive step has led to regioselective catalytic transformations of propargylic derivatives via carbon(l)-atom bond formation or alternately to propargylation. Due to their rearrangement into indenylidene complexes, metal-allenylidene complexes were also found to be catalyst precursors for olefin and enyne metathesis. 

The first nonambiguous report of rearrangement of esters derived from propargyl alcohols promoted by silver salts was due to Saucy and coworkers at Hoffmann-La Roche.50 Their observations on the transformation of acetate derived from... 

Doubly (and even triply) charged anions appeared on the horizon of organic chemistry relatively recently, They were immediately recognized as extremely useful intermediates due to the synthetic opportunities offered by their unique pattern of reactivity. Besides the dianion 174, the dianions of carboxylic acids 178 (Scheme 2.82), propargylic dianion 179, and the dianion 180 derived from propargyl alcohol are now widely used as nucleophiles. Selectivity in electrophilic attack for these species is governed in much the same way as was described for 174 the least-stabilized anionic center is the preferential site of attack by the electrophile (marked with an asterisk in Scheme 2.82). 

Enantio-enriched axially chiral allenyltitanium compounds have been synthesized from optically active propargyl alcohol derivatives by the reaction with a divalent titanium reagent, TKOPfj MgXPr1, and their reactions with a variety of electrophiles have been studied.285... 

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