摘要:

The new anions [R3M′M(CO)5]−(R3M′ = Ph3Si, MePh2Si, Ph3Ge, Ph3Sn, Me3Sn, and Ph3Pb; M = Cr, Mo, W) have been prepared as tetraethylammonium salts by reaction of R3M′Li with [Et4N(ClM(CO)5]. The redistribution reaction between [Ph3SnW(CO)5]−and [Cl3SnW(CO)5]−affords [PhCl2SnW(CO)5]−or [Ph2ClSnW(CO)5]−. Anhydrous HCl reacts with [Ph3SiW(CO)5]−and [Ph3GeW(CO)5]−to form [ClW(CO)5]−but with [Ph3SnW(CO)5]−to form [Cl3SnW(CO)5]−. An insertion reaction of SnBr2with [BrW(CO)5]−forms the new anion [Br3SnW(CO)5]−while SnCl2and GeCl2(from HGeCl3) react with [ClM(CO)5]−to produce the known species [Cl3M'M(CO)5]−(M′ = Ge, Sn; M = Cr, Mo, W). Infrared spectra in the carbonyl stretching region are reported for all anions.

ISSN:0008-4042    

DOI:10.1139/v75-065

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The reaction of sodium diethylphosphonate NaOP(OC2H5)2with the mesylates ofcisandtrans-4-t-butyl cyclohexanols has been studied in toluene, dioxane, and dimethylformamide (DMF). Beside the products expected from the reaction (elimination and P-alkylation products originating from initial O-attack have been isolated. This latter reaction competes with P-alkylation (normal Michaelis–Becker reaction) and is the only substitution reaction in DMF. Results are interpreted in terms of the HSAB (Hard and Soft Acids and Bases) theory and by preferential solvation. Since the substitution products are of inverted configuration, the SN2 mechanism seems to be well substantiated.

ISSN:0008-4042    

DOI:10.1139/v75-066

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The photolysis of methylvinylsulfide in the 230–270 nm region yields products which can be explained by the following primary reactions.The methyl and vinyl radicals are titrated by the addition of methyl mercaptan to the system.At short photolysis time, the sum of the methane and ethylene quantum yields is near unity.

ISSN:0008-4042    

DOI:10.1139/v75-067

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

3- and 4-Hydroxypyridines exist in their enolic form, in the gas phase, as evidenced by the similarity of the deuterium isotope effects on the loss of CO, calculated on nearly equimolar mixtures of HO- and DO-pyridines. This is confirmed by analysis of metastable ratios evaluated on hydroxypyridine fragment ions and on the same ions produced by direct ionization. 2-Hydroxypyridine shows a weaker isotope effect for the same reaction and this is confirmed by the study of an equimolar mixture of 2-ethoxy- and 2-ethoxy-d5-pyridines. It is shown that 2-hydroxypyridine also exists as its enolic form, in the gas phase.

ISSN:0008-4042    

DOI:10.1139/v75-068

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Chlorinolysis of an anhydropenicillin affords a 2-(2′-chloro-3′S-amino, -acylamino or -phthalimido-4′-oxo)azetidinyl-3-methyl-2-butenoyl chloride, as a mixture of 2′R(cis) and 2′S(trans) epimers in which the 2′Repimer usually predominates. Hydrolysis of the acid chloride and treatment of the carboxylic acid with aqueous bicarbonate causes cyclization, in the case of a 3′-acylamino substituent, to a 2R-6-(1′-carboxy-2′-methyl-prop-1-enyl)-1-oxa-3,6-diaza-4S,5R-bicyclo[3,2,0]hept-2-ene-7-one. The mechanisms of these transformations are discussed, and alternative routes to such fused oxazoline–azetidinones are also presented.The oxazolines undergo ready hydrolysis to sulfonic acid salts of 2-(2′R-acyloxy-3′S-amino-4′-oxo)azetidinyl-3-methyl-2-butenoates upon treatment with the hydrate of a sulfonic acid in acetone solvent. Neutralization of these salts proceeds without O → N acyl transfer, because acylation yields a diacylated azetidinone in which the new acyl substituent is attached to nitrogen. Monobromination of the allylic methyl groups of these salts, followed by treatment with 2 molar-equiv. of triethylamine, leads to a deep-seated rearrangement, in high yield, to an oxazinone. The mechanism of this rearrangement and, in particular, the role of acylimines in this and related reactions, including the biosynthesis of penicillin, are discussed.

ISSN:0008-4042    

DOI:10.1139/v75-069

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Deacylation of unsubstituted and ofo-F-,m-F,p-F, α-F, pentafluoro-,p-methyl-, andp-trifluoromethyl-substitutedtrans-cinnamoyl- α-chymotrypsins has been studied from pH4 to 8. The deacylation rate constants were found to depend upon the ionization state of a group on the enzyme with an apparent pKin the range 6.3–7.3. The hydrolysis rates of the correspondingly substitutedp-nitrophenylcinnamate esters were determined at pH10.6. Correlation of the data for these model reactions with the corresponding rates of enzyme deacylation suggests that thep-methyl-substituted acylenzyme is about an order of magnitude more reactive than expected whilep-trifluoromethyl substitution results in deacylation at a rate 10 times slower than expected. The remaining substituents exert about the anticipated rate effect on deacylation.

ISSN:0008-4042    

DOI:10.1139/v75-070

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Sodium borohydride reduction of the 1,2(lH)-diazepines1a-eand7, and the 1,2(1H)-diazepine iron tricarbonyl complexes4a–bprovides the 2,3-dihydro-1,2(1H)-diazepines2a–eand8, and the (2,3-dihydro-1,2(1H)-diazepine)Fe(CO)3derivatives5a–b, respectively. Fe(CO)3complexes5aand6amay be also directly obtained from the 1,2(1H)-diazepines2aand3a, respectively. A number of diacylated compounds (3a–c,6a–b, and9) are prepared some of which (2a,3a,8, and9) are readily converted into their corresponding (4 + 2)π cycloadducts (14a–d). Treatment of the borohydride reduction products2a–cwith sodium methoxide in methanol gives the 3,4-dihydro-1,2(2H)-diazepines15a–c. Acetylation of15aaffords the 2-acetyl derivative16awhich may also be prepared by sodium methoxide deacetylation of either3aor9. 2-Tosyl-3,4-dihydro-1,2(2H)-diazepine (18) is obtained from2aby a similar tosylation and deacetylation sequence. When either2aor3aare subjected to sodium methoxide in methanol-O-d, compounds15aand16a, respectively, are produced which show high deuterium incorporation at C4and C6(n.m.r. analysis). Photolysis of the 2,3-dihydro-1,2(1H)-diazepines2a,3a,8, and9and the 3,4-dihydro-1,2(2H)-diazepine16aaffords the unstable 2,3-diazabicyclo[3.2.0]hept-6-ene23a,23b,25a, and25band 1,2-diazabicyclo[3.2.0]hept-6-ene27derivatives, respectively. Treatment of either25aor25bwith sodium methoxide results cleanly in N2-deacylation to give compound26.

ISSN:0008-4042    

DOI:10.1139/v75-071

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The electrochemical oxidation of substituted malonic acid half-esters was studied in the presence of trifluoroacetic acid. Some 'crossed' Kolbe products were obtained together with some unsaturated carboalkoxy compounds, trifluoromethylated adducts to the double bond, and trifluoromethylated dimers.The electrolysis of trifluoroacetic acid in the presence of olefinic carboalkoxy compounds was also studied.

ISSN:0008-4042    

DOI:10.1139/v75-072

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The Diels–Alder adducts of cyclopentadiene and azodiacyls or azodiaroyls isomerize to 1,3,4-oxadiazines at rates which show a trend qualitatively related to the rotation rates of the correspondingN,N-dimethylamides. The isomerizations probably occur by a cyclic concerted mechanism.The ring substituents in the adducts of 1,4-dimethyl-2,3-diphenylcyclopentadiene and azodibenzoyl or azodiacetyl accelerate the isomerization; the kinetic evidence supports a cyclic intermediate in the reaction in isooctane as solvent but is more consistent with a dipolar intermediate in aqueous ethanol.Some generalizations about the effect of substituents on the isomerization are presented on the basis of these and earlier experiments.

ISSN:0008-4042    

DOI:10.1139/v75-073

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

To serve as models of protein–nucleic acid complexes, annealed complexes of several sequential lysine–glycine polypeptides with DNA have been formed. Circular dichroic spectra of the DNA contained in the complexes indicates that several discrete conformations of DNA can exist when complexed.

ISSN:0008-4042    

DOI:10.1139/v75-074

出版商:NRC Research Press    

年代:1975

数据来源: NRC