Reductive cleavage by metallic sodium in liquid ammonia of cotton lignin

L. S. Smirnova; S. A. Mukhamedova; Kh. A. Abduazimov

doi:10.1007/bf00597720

REDUCTIVE CLEAVAGE WITH METAL IN LIQUID AMMONIA: I. THE SELECTIVE CLEAVAGE OF THE BENZYLTHIO C—S BOND VERSUS THE BENZYLIDENEDIOXY C—O BOND IN METHYL S-BENZYL-4,6-O-BENZYLIDENE-2-THIO-α-D-ALTROPYRANOSIDES; THE INFLUENCE OF THE COSOLVENT 1,2-DIMETHOXYETHANE ON THE COURSE OF THE REACTION

Canadian Journal of Chemistry ◽

10.1139/v66-080 ◽

1966 ◽

Vol 44 (5) ◽

pp. 591-602 ◽

Cited By ~ 8

Author(s):

U. G. Nayak ◽

R. K. Brown

Keyword(s):

Infrared Absorption ◽

Liquid Ammonia ◽

Reductive Cleavage ◽

The Other ◽

Metallic Sodium ◽

Absorption Bands ◽

Strong Band ◽

The One ◽

Infrared Absorption Bands ◽

Phenyl Moiety

The improved solubility of methyl S-benzyl-4,6-O-benzylidene-2-thio-α-D-altropyranoside (1) in liquid ammonia diluted with 1,2-dimethoxyethane has permitted the selective cleavage by metallic sodium or lithium of the C—S bond to give methyl 4,6-O-benzylidene-2-thio-α-D-altropyranoside in 70–75% yield. On the other hand, the slight solubility of I in liquid ammonia alone results only in the completely hydrogenolyzed material, methyl 2-thio-α-D-altropyranoside, along with unchanged I.Generally, in liquid ammonia alone, reductive cleavage is rapid (15–20 min) and the benzylidene and benzyl groups are converted largely into toluene accompanied by a small amount of bibenzyl. In liquid ammonia – 1,2-dimethoxyethane mixtures the reaction is much slower (≥ 1.5 h); under these conditions the benzylidene and benzyl groups are converted to a larger extent into bibenzyl, the rest becoming toluene.The two strong infrared absorption bands (in Nujol) in the region of 766 to 778 cm−1 and 706 to 718 cm−1 have been assigned to the phenyl moiety of the benzylidene group, and the one strong band in the region of 702 cm−1 to the phenyl moiety of the S-benzyl group.

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Reductive cleavage with metal in liquid ammonia. II. Olefin formation in attempts at selective cleavage of methyl S-benzyl-4,6-O-benzylidene-3-O-methyl-2-thio-α-d-altropyranoside and its S-methyl analogue by sodium metal in liquid ammonia diluted with 1,2-dimethoxyethane

Canadian Journal of Chemistry ◽

10.1139/v67-083 ◽

1967 ◽

Vol 45 (5) ◽

pp. 481-494 ◽

Cited By ~ 10

Author(s):

U. G. Nayak ◽

M. Sharma ◽

R. K. Brown

Keyword(s):

Liquid Ammonia ◽

Mixed Solvent ◽

Reductive Cleavage ◽

Metallic Sodium ◽

Reaction Conditions ◽

Sodium Metal ◽

Alkaline Reaction

When methyl S-benzyl-4,6-O-benzylidene-3-O-methyl-2-thio-α-d-altropyranoside (VI) in liquid ammonia was treated with metallic sodium, a reductive cleavage occurred to give methyl 3-O-methyl-2-thio-α-d-altropyranoside in an 85% yield. In the solvent 1,2-dimethoxy-ethane, the reaction of sodium with VI gave little, if any, reductive cleavage. Instead, a base-catalyzed elimination of methanol took place to give the two olefins methyl,S-benzyl-4,6-O-benzylidene-2,3-didehydro-3-deoxy-2-thio-α-d-erythro-hexopyranoside (IX) and S-benzyl-4,6-O-benzylidene-l,2-didehydro-1-deoxy-3-O-methyl-2-thio-d-ribo-hexopyranose (X). Under the alkaline reaction conditions, IX isomerized partly to a third olefin, methyl.S-benzyl-4,6-O-benzylidene-3,4-didehydro-3-deoxy-2-thio-α-d-erythro(threo)-hexopyranoside (XI).In the mixed solvent liquid ammonia and 1,2-dimethoxyethane, sodium reacted with VI to give a 33% yield of the 2,3-olefin IX. Other products, no doubt present, were not isolated in this experiment.Three analogous olefins were obtained from the reaction of sodium or basic reagents with methyl 4,6-O-benzylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside (VIa) in 1,2-dimethoxyethane.

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Reductive cleavage with metal in liquid ammonia. III. Olefin formation from the reaction of sodium metal with methyl 4,6-O-ethylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside dissolved in 1,2-dimethoxyethane

Canadian Journal of Chemistry ◽

10.1139/v67-285 ◽

1967 ◽

Vol 45 (15) ◽

pp. 1767-1775 ◽

Cited By ~ 2

Author(s):

U. G. Nayak ◽

M. Sharma ◽

R. K. Brown

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Liquid Ammonia ◽

Reductive Cleavage ◽

Metallic Sodium ◽

Sodium Metal ◽

Infrared Data ◽

Nuclear Magnetic

Methyl 4,6-O-ethylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside, when heated in refluxing 1,2-dimethoxyethane with an equimolar quantity of metallic sodium, gave approximately a 75% yield of a mixture of the three olefins, methyl 2,3-didehydro-3-deoxy-4,6-O-ethylidene-S-methyl-2-thio-α-d-altropyranoside (XI), l,2-didehydro-l-deoxy-4,6-O-ethylidene-3-O,S-dimethyl-2-thio-d-ribo-hexopyranose (XII), and methyl 3,4-didehydro-3-deoxy-4,6-O-ethylidene-S-methyl-2-thio-α-d-erythro(or threo)-hexopyranoside (XIII) (tentative). Only compounds XI and XII could be separated and characterized. The structural assignments were based on a comparison with authentic samples and on nuclear magnetic resonance and infrared data, as well as on a comparison with the characteristics of analogous 4,6-O-benzylidene compounds previously reported (2).

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