2-Aryloxytetrahydrofurans. Their Reductive Cleavage by Ether Solutions of AlH2Cl and their Cleavage and Rearrangement by Ether Solutions of AlCl3

1972 ◽  
Vol 50 (22) ◽  
pp. 3639-3647 ◽  
Author(s):  
P. C. Loewen ◽  
R. K. Brown
Keyword(s):  
Electron Donor ◽  
Bond Cleavage ◽  
Reductive Cleavage ◽  
Para Position ◽  
Ring Cleavage ◽  
Electrophilic Attack ◽  
Aryl Ring ◽  
Excellent Yield ◽  
Acid Catalyzed

The hydrogenolysis of 2-aryloxytetrahydrofurans by excess AlH2Cl gave, in excellent yield, only those products expected from exo C—O bond cleavage regardless of the nature of the substituent in the aryl ring. None of the 4-aryloxy-1-butanol, the product expected from ring cleavage, was detected. The reaction was very much faster than the corresponding AlH2Cl hydrogenolysis of 2-alkoxytetrahydrofurans which is known to give only ring cleavage products under similar conditions.Treatment of 2-aryloxytetrahydrofurans or pyrans with AlCl3 in ether, resulted in acid-catalyzed cleavage to the corresponding phenol and dihydrofuran or dihydropyran, the latter immediately forming polymeric products. For those 2-aryloxytetrahydrofurans or pyrans, unsubstituted, or substituted with electron donor groups in the aryl ring, another product was obtained which resulted from electrophilic attack of one protonated dihydrofuran or pyran on the ortho or para position of the phenol. These rearrangement products were also obtained in small amounts as byproducts when 2-aryloxytetrahydrofurans were hydrogenolyzed with insufficient AlH2Cl.

THE INFLUENCE OF SUBSTITUENTS ON THE EASE AND DIRECTION OF RING OPENING IN THE LiAlH4–AlCl3 REDUCTIVE CLEAVAGE OF SUBSTITUTED 1,3-DIOXOLANES

1964 ◽  
Vol 42 (5) ◽  
pp. 990-1004 ◽  
Author(s):  
B. E. Leggetter ◽  
R. K. Brown
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Ring Opening ◽  
Room Temperature ◽  
Reductive Cleavage ◽  
The Other ◽  
Ring Cleavage ◽  
Other Hand ◽  
Influence Of Substituents

The room temperature hydrogenolysis by LiAlH4–AlCl3 of ether solutions of a number of 1,3-dioxolanes has been studied.Electron donor substituents on the C2 atom of the ring accelerate while electron acceptor substituents on C2 retard the reductive ring cleavage. The same effect but to a lesser extent is observed when these substituents are attached to the C4 or C5 atom of the ring.When electron donor substituents are attached to C4, ring cleavage occurs predominantly at the C2—O bond remote from the C4 position. On the other hand, electron-withdrawing groups attached to C4 give predominantly scission of the C2—O bond closer to the C4-substituted position. In contrast to this marked control over the direction of ring cleavage exhibited by substituents on C4, those on C2 generally have little or no effect on the direction of ring opening.A mechanistic interpretation of the results is presented.

Benzyl ethers of methyl α-D-glucopyranoside

1980 ◽  
Vol 45 (7) ◽  
pp. 1959-1963 ◽  
Author(s):  
Dušan Joniak ◽  
Božena Košíková ◽  
Ludmila Kosáková
Keyword(s):  
Kinetic Study ◽  
Spectrophotometric Determination ◽  
Reductive Cleavage ◽  
Ether Bond ◽  
Benzyl Ethers ◽  
Acid Catalyzed ◽  
Model Substances ◽  
Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

Bond cleavage in acid-catalyzed hydrolysis of vinyl phosphates

1972 ◽  
Vol 94 (10) ◽  
pp. 3676-3677 ◽  
Author(s):  
Edward P. Lyznicki ◽  
Thomas T. Tidwell
Keyword(s):  
Bond Cleavage ◽  
Acid Catalyzed ◽  
Hydrolysis Of

ChemInform Abstract: Metal-Free Reductive Cleavage of N-O Bonds in Weinreb Amides by an Organic Neutral Super-Electron Donor.

ChemInform ◽  
2008 ◽  
Vol 39 (52) ◽  
Author(s):  
Sylvain P. Y. Cutulic ◽  
John A. Murphy ◽  
Hardeep Farwaha ◽  
Sheng-Ze Zhou ◽  
Ewan Chrystal
Keyword(s):  
Electron Donor ◽  
Reductive Cleavage ◽  
Metal Free ◽  
Weinreb Amides

The Influence of the 2-Alkoxy Group and of C-5 Substituents on the Direction of Reductive Cleavage of 2-Alkoxytetrahydrofurans by AlH2Cl in Ether Solution

1972 ◽  
Vol 50 (10) ◽  
pp. 1502-1512 ◽  
Author(s):  
P. C. Loewen ◽  
Miss L. P. Makhubu ◽  
R. K. Brown
Keyword(s):  
Transition State ◽  
Alkyl Group ◽  
Steric Effect ◽  
Bond Cleavage ◽  
Alkoxy Group ◽  
Ring Cleavage ◽  
Relative Ease ◽  
Ether Solution ◽  
A Minor ◽  
Minor Extent

The AlH2Cl hydrogenolysis of ether solutions of 2-alkoxytetrahydrofurans in which the alkoxy group is either CH3O, C2H5O, i-C3H7O, or t-C4H9O, gives only those products resulting from ring C—O bond cleavage. However, substituents at C-5 of 2-methoxytetrahydrofuran exert a strong effect on the ratio of ring to exo C—O bond cleavage. Thus, alkyl (electron donor) groups at C-5 promote an increase in the amount of exo cleavage, the proportion increasing from 62.5 to 100% as the C-5 alkyl group is changed from CH3 to t-C4H9. In contrast, electron withdrawing substituents, CH3OCH2— and C6H5, at C-5 favor ring cleavage to the extent of 93 and 84% respectively.The results are interpreted in terms of the influence that these substituents exert through their electronic properties on the relative ease of attainment of the transition state leading to either ring C—O or exo C—O bond cleavage. However, evidence is provided to show that the bulk steric effect of these substituents also controls, though to a minor extent, the proportion of ring to exo cleavage.

Acid-catalyzed acylation reaction via C–C bond cleavage: a facile and mechanistically defined approach to synthesize 3-acylindoles

2014 ◽  
Vol 50 (81) ◽  
pp. 12181-12184 ◽  
Author(s):  
Qi Xing ◽  
Pan Li ◽  
Hui Lv ◽  
Rui Lang ◽  
Chungu Xia ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Acylation Reaction ◽  
Acid Catalyzed
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