Alcohol From ester

Preparation of Tertiary Alcohols from Esters and Grignard Reagents... 

PREPARATION OF TERTIARY ALCOHOLS FROM ESTERS AND GRIGNARD REAGENTS... 

Studies of reductions with metal hydndes have concentrated on improvements in selectivity or conditions Replacement of the usual lithium aluminum hydnde-ether combination with potassium borohydride-methanol results m high yields of alcohol from ester [76] and less hazard [77] (equation 62) Reduction of a... 

This compound can disproportionate, generating silane (SiH4) which is liable to be pyrophoric. Presumably other alkoxy silanes can do likewise [ 1 ]. Its use as a reducing agent for the preparation of alcohols from esters is considered safer in air than under... 

Both older methods for the reduction of esters to alcohols, catalytic hydrogenation and reduction with sodium, have given way to reductions with hydrides and complex hydrides which have revolutionized the laboratory preparation of alcohols from esters. 

Porter et al. studied the photorelease of various alcohols from ester 65, which release their alcohol moiety and form lactones 67 and 68 in solvents with abstractable H-atoms (Scheme 36). They also reported that the photorelease from 65 could be initiated by electron transfer from amines. We used transient spectroscopy to elucidate the photorelease mechanisms of 65 in 2-propanol. Laser flash photolysis of 65 resulted in the formation of the triplet excited state of 65, which has a A ax at 330 and 530 nm. The triplet excited state of 65 decayed with a rate constant of 3 x 10 s in 2-propanol to form radical 66. The quantum yield for photorelease from 65 was determined to be 0.62 in 2-propanol. 

Alcohols from esters. The major problem is reaction selectivity. Paraffin by-product in alcohol results if the catalyst activity is too high. Yet the reduction of esters to alcohols is a difficult reaction. Copper chromite catalyst, 3000-5000 psig hydrogen, and a temperature of 270-300°C are required for the reduction. An alternate catalyst is CuO/ZnO, which is used for methyl ester reduction only. Hydrogen solubility in alcohol is limiting. 

Related Methods Esters from Alcohols (Section 123) Alcohols from Ethers (Section 39) Esters from Alcohols (Section 108) Alcohols from Esters (Section 38)... 

This is an extremely important reaction, and one of the best ways of making alcohols from esters. Stopping the reaction at the aldehyde stage is more difficult we shall discuss this in Chapter 24. 

We need carbonyl groups to do conjugate addition so the tertiary alcohols will have to be made from them. In Chapter 9 (p. 222) we saw how to make such tertiary alcohols from esters and organometallic compounds and in Problem 1 of this set we saw how to do double conjugate additions on unsaturated esters - all the pieces fit together. 

NaAlH4 [CB5] or LAH-N-methylpyrrolidine [FSl] is also an efficient reducing agent, as is excess AlHj EtjN [CB7], All these reductions are run in THF at 0°C or at r.t. Ate complexes formed from DIBAH and -BuLi in THF-hexane at r.t. also give alcohols from esters [KAl]. Red-Al in petroleum ether allows the selective reduction of long-chain bromoesters to bromoalcohols [W8],... 

Alexander Saytzev was born in Kazan in Russia on 20 June 1841. He studied in Germany at Marburg and Leipzig and with Butlerov at Kazan. In fact both Saytzev and Markovnikov were students of Butlerov, Saytzev became Profe.ssor of Chemistry at the University of Kazan, where he worked on the synthesis of alcohols from esters, ketones and aldehydes using zinc and alky] halides. His student Reformatsky continued his work. Saytzev s brother Mikhayl was also a chemist and ran the chemical works in Kazan. 

Alexander Mikhaylovich Saytzev (Saytzeff) (Kazan 20 June 1841 (O.S.)-2 September 1910) studied with Kolbe in Marburg and Leipzig, and was professor in the University of Kazan. He discovered the synthesis of primary and secondary alcohols from esters, ketones, and aldehydes by the action of zinc and alkyl iodides (see Reformatsky, p. 858). He also discovered aliphatic sulphoxides. His brother Mikhayl Mikhaylovich (b. Kazan, 30 August 1845), at first his assistant and later manager of a chemical works in Kazan, discovered the reduction of acid chlorides to aldehydes by hydrogen gas in presence of palladium. ... 

Further examples of the reaction RCOOR — RCOOH + R OH are included in section 38 (Alcohols from Esters) and section 30A (Protection of Carboxylic Acids)... 

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