Reduction with Metal Hydrides. XII. Reduction of Acetals and Ketals with Lithium Aluminum Hydride-Aluminum Chloride

The relative ease of hydrogenolysis of ether solutions of acetals or ketals is much greater with AlHzCl than with AlH3. Conversion of the species AlHs & AlHzCl P AlHClz one into the other is fast, and is accomplished by the addition of the appropriate quantity of AlC13 or LiAIH4 to solutions of HlH8 or AlHC12, respectively. Gradual addition of an equimolar proportion of AlCla in ether to an ether solution of equimolar roportions of LiAlH4 and acetal or ketal first forms AlHa, which is rapidly converted into & H~C I as more AlCl3 is added. During the time of this addition (210 min) little reduction by AlH3 takes place. Most of the reduction is done by the species AlHzCl when the AlCl3 is completely added.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The major reducing species operative when an equimolar proportion of AlCl₃ is added over a short period of time to an ether solution of equimolar proportions of LiAlH₄ and acetal or ketal

Diner¹,

Davis²,

Brown³

1967

“…Benzyl alcohols which were not commercially available and the a,a-dideuterated analogues of the benzyl alcohols were prepared by reduction of the corresponding benzoic acid or the methyl ester (65,66). …”

Section: Methodsmentioning

confidence: 99%

Solvolysis of 2-substituted-9-(otrho-substituted phenylmethyl)fluoren-9-yltrimethylammonium ions in various solvents. The effect of steric crowding on alkene formation

Smith¹,

Pradhan²

1986

The solvolytic reaction of several 9-(ortho-substituted phenylmethy1)fluoren-9-yltrimethylammonium salts has been investigated in several different solvents. Substitution and elimination products were found for the reactions in all the solvents studied, with the exceptions that reaction in both tert-butyl alcohol and chloroform led exclusively to the alkene product. The observed rate constants for alkene formation and the percent alkene were measured and it was found that the di-ortho compounds reacted at a faster rate but produced less alkene than the reaction of the corresponding mono-ortho salts. Hydrogen-deuterium isotope effects were also determined for the various reactions. The results are discussed in terms of the reaction proceeding by way of the El mechanism, where steric acceleration promotes the loss of the bulky ammonium leaving group to give the carbocation intermediate. Op6rant dans plusieurs solvants, on a, ktudik la &action solvolytique de plusieurs sels trimkthylammonium des (phknylmkthyles substituks en ortho)-9 fluorbne-9 yles. A l'exception des rkactions dans l'alcool tert-butylique ou dans le chloroforme, toutes les rkactions ktudikes dans les autres solvants ont conduit L la formation de produits de substitution ainsi que d'klimination. On a mesurk les constantes de vitesse pour la formation des alcbnes ainsi que les pourcentages d'alcbnes formks; on a trouvk que les composks doublement substituks en ortho dagissent plus rapidement mais qu'ils produisent moins d'alcbnes que les rkactions des sels correspondants qui ne portent qu'un substituant en ortho. On a dkkrmink les effets cinktiques hydrogbne-deutkrium pour diverses &actions. On discute des ksultats en fonction d'une reaction qui se produirait par le biais d'un mkcanisme E l et dans lequel l'accklkration stkrique favoriserait le perte du nuclkofuge ammonium encombrant au profit de la formation d'un carbocation intermkdiaire. PETER JAMES SMITH[Traduit par la revue]

“…However, in the presence of Lewis acids, these acetals and ketals are hydrogenolized by lithium alunlinunl hydride to the corresponding ethers. Cyclic acetals and ketals under these conditions yield hydroxy ethers (2,3,4).…”

Section: Introductionmentioning

confidence: 90%

THE RELATIVE EASE OF REDUCTIVE CLEAVAGE OF 1,3-DIOXOLANES AND 1,3-DIOXANES IN ETHER SOLUTION BY LiAlH₄–AlCl₃

Leggetter¹,

Diner²,

Brown³

1964

In ether solution, 1,3-diosolanes are hydrogenolyzed faster by LiAII-Id-AlCl3 than are the corresponding 1,3-dioxanes. This difference is attributed to the relative ease of oxocarbonium ion formation in the rate-determining step of the reaction. The results obtained have been utilized to explain the selective cleavage of the five-and six-membered acetal structures found in the polyacetals of hexitols.