摘要:

The products obtained when α-(o-nitrophenylthio) acids are reduced by means of sodium borohydride and palladium–charcoal depend on (a) the reaction temperature, (b) the solvent, (c) the length of time in which the α-(o-nitrophenylthio) acid is in contact with the reducing agent, and (d) the nature of the substituents on the α-(o-nitrophenylthio) acid. By varying these conditions, benzothiazine hydroxamic acids (i.e. substituted 3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazines), the corresponding lactams (3,4-dihydro-3-oxo-2H-1,4-benzothiazines), and derivatives of 2-carboxymethylthioazobenzene can be prepared.In two cases, additional products were obtained. When (o-nitrophenylthio)acetic acid was catalytically reduced for 30 min in dioxane, 3,4-dihydro-3-oxo-2H-1,4-benzothiazine-1,1-dioxide (VIc) was an unexpected product, and when α-(4-trifluoromethyl-2-nitrophenylthio)-isobutyric acid was left for a prolonged time in contact with sodium borohydride and palladium–charcoal, a derivative of hydrazobenzene, namely, 2-carboxy(α,α-dimethyl)methylthio-5-trifluoromethylhydrazobenzene (V), was one of the three identified products.

ISSN:0008-4042    

DOI:10.1139/v66-262

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

At temperatures above 175° and with packed columns, rearrangement of allyl 2,6-dichlorophenyl ether occurs during gas–liquid chromatographic analysis with a contact time of no more than 4 min. For example, at a temperature of 205° with Gas Chrom P as packing material, about 7% of the ether is changed, but the packing 20% Apiezon L on Gas Chrom P increases this to about 50%. Products characteristic of both thermal and acid-catalyzed rearrangements are obtained. The number of such products increases to a maximum of five as the temperature is increased to 228°.Accordingly, the results of gas–liquid chromatographic analysis of mixtures obtained from the Claisen rearrangement of allyl phenyl ethers must be interpreted with care if unchanged ether is present.

ISSN:0008-4042    

DOI:10.1139/v66-263

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Neutral polysaccharides can be oxidized by lead tetraacetate in dimethyl sulfoxide if 15–20% of glacial acetic acid is added to prevent oxidation of the solvent. The oxidation proceeds at a rate which is several times faster than that of periodate oxidation in aqueous solution, and the same amount of oxidant is consumed. Polysaccharides oxidized by lead tetraacetate in dimethyl sulfoxide can be recovered in excellent yield by precipitation with alcohol, and have been shown to contain free aldehyde groups. Identification of the products of reduction and hydrolysis of the oxidized polysaccharides showed that the oxidation followed the normal glycol-cleavage pattern given by lead tetraacetate in other solvents. Addition of potassium acetate to the oxidations in dimethyl sulfoxide decreased the consumption of lead tetraacetate by dextran (mainly α-(1 → 6) and α-(1 → 4)). Reduction and hydrolysis of dextrans oxidized in the presence and absence of potassium acetate yielded glycerol and erythritol in the respective ratios of 3.8:1 and 8.7:1. This result indicated that potassium acetate inhibited oxidation of the C-3, C-4 glycol groups in the dextran. Acidic polysaccharides behaved atypically in this oxidation system, and those containing a high proportion of uronic acid units were resistant to oxidation.

ISSN:0008-4042    

DOI:10.1139/v66-264

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The products obtained by the periodate oxidation of methyl α- and β-D-xylopyranosides have been examined by nuclear magnetic resonance spectroscopy. In deuterium oxide each product exists mainly in two forms, one of which is a hydrated dialdehyde and the other a hemialdal (1,4-dioxane derivative). In dimethyl sulfoxide the dialdehyde cyclizes slowly to yield the hemialdal which, at equilibrium, is found to be by far the most stable of the many isomeric forms possible. The spectrum of this hemialdal in both solvents provides an example of a degenerate ABX type of pattern. The spectra of the products prepared from 5-deuterated xylosides show that the 1-methoxyl group of each hemialdal is axial and the 4-hydroxyl group equatorial, and that the one derived from the β-anomer possesses an inverted chair conformation relative to that of the other hemialdal and of the glycoside itself. The 2-hydroxyl group of each hemialdal appears to be axially oriented. The data support the long-standing view that glycol scission of anomeric aldopentopyranosides leads to products that are mirror images.It has been found also that each product yields a mixture of severalp-nitrobenzoates.

ISSN:0008-4042    

DOI:10.1139/v66-265

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The homolytic phenylation of 3- and 4-picoline under the conditions of the Gomberg–Hey reaction has been studied quantitatively. The methyl group in both picolines was found to activate the nucleus to the same extent. All the nuclear positions in both systems, except for C5in 3-picoline, were slightly activated as compared with any one position in benzene. The significance of these results is discussed.

ISSN:0008-4042    

DOI:10.1139/v66-266

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The rate constants for the perchloric acid catalyzed substitution of one ethylthio group of 2,3,4,5,6-penta-O-acetyl-D-glucose diethyl dithioacetal (Va) and the acetoxy group bonded to C1of 1,2,3,4,5,6-hexa-O-acetyl-D-glucoseS-ethyl monothioacetal (VIa) have been measured when the substrates were dissolved in solutions of acetic acid and acetic anhydride. The rate-determining step is interpreted to be the dissociation of the substrate conjugate acid to give a carbonium–sulfonium cation. The rate constants indicate that acyclic sugar derivatives are substituted faster than cyclic (pyranose) derivatives, and that an acetoxy group is substituted faster than an ethylthio group.

ISSN:0008-4042    

DOI:10.1139/v66-267

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v66-268

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Thecis- andtrans-isomers of 1,2-O-(2′-hydroxyethylidene)-glycerol (I and II) and 1,2-O-(hydroxyisopropylidene)-glycerol (V and VI) were prepared and their configurations assigned by stereospecific chemical synthesis. Equilibration of 1,2-O-(2′-cis-hydroxyethylidene)-L-glycerol (I) in acidified chloroform gave mainly 1,3-O-(2′-cis-hydroxyethylidene)-glycerol (III). In the 1,2-O-(hydroxyisopropylidene)-glycerol series, equilibration data and infrared absorption studies showed that hydrogen bonding of theO-(hydroxyisopropylidene) hydroxyl group was more pronounced in thecis-isomers.

ISSN:0008-4042    

DOI:10.1139/v66-269

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

3,4-Methylenedioxy-6-aminophenoil(I) and 3,4-dimethoxy-6-aminophenol (IV) were condensed with various α-ketoesters to give the corresponding 6,7-methylenedioxy- and 6,7-dimethoxy-1,4-benzoxazin-2-ones.

ISSN:0008-4042    

DOI:10.1139/v66-270

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A by-product isolated in low yield from the reaction ofp-chlorobenzyl chloride with potassium thiocyanate and sodium iodide in dimethylformamide was shown to be the isotrithiocyanuric acid derivative I (R = p-chlorobenzyl). I gave the isodithiocyanuric acid ester (III) on alkaline hydrolysis, and mono-p-chlorobenzyl isotrithiocyanurate (IV) on reduction with sodium hydrosulfite. Treatment of I with sodium hypochlorite in aqueous alcoholic medium resulted in the direct replacement of the sulfhydryl group by an alkoxyl group. TheN,S,S-triester VIII rearranged, on heating, to the symmetricalS,S,S-triester IX; this behavior is opposite to that shown by the oxygen analogues.

ISSN:0008-4042    

DOI:10.1139/v66-271

出版商:NRC Research Press    

年代:1966

数据来源: NRC