摘要:

A study of the condensation of keten acetals with some halonaphthoquinones has led to the simple and regiospecific synthesis of some naturally occurring anthraquinones: catenarin, helminthosporin, emodin, and chrysophanol. The results show unambiguously that a previously proposed mechanism is erroneous. The reaction of these acetals with chloromaleic anhydride also provided a one-step preparation of some substituted phthalic anhydrides.

ISSN:0008-4042    

DOI:10.1139/v74-011

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The authors propose two new solutions to the problem of the synthesis of 3-methylfuranquinones. The methods have the advantage of requiring readily accessible substrates and reagents. A new synthesis of tanshinoneI(26) illustrates one of the processes which in principle should also be applicable to the preparation of isotanshinones. Several novel transformations have been observed in the course of this study.

ISSN:0008-4042    

DOI:10.1139/v74-012

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Matrix infrared and laser Raman spectra are reported for GeF2and (GeF2)2in both N2and Ar matrices. Raman depolarization measurements for the monomer in N2matrices identify ν1at 653 cm−1. Warm-up experiments identify infrared and Raman lines at 665, 478 cm−1and 669, 465, and 424 cm−1respectively, with the first stage of the polymerization of GeF2monomer and are assigned to GeF stretching modes of the dimer (GeF2)2, having a centrosymmetricC2h, non-planar structure, containing a double fluorine bridge similar to the structure proposed for (SeO2)2. A normal coordinate analysis is performed on the dimer using a force field transferred from the monomer. The results provide additional evidence for the correctness of the vibrational and stereochemical assignments for the dimer.

ISSN:0008-4042    

DOI:10.1139/v74-013

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The u.v. absorption spectrum of 1,2,5-selenadiazole in the 3050–2600 Å region has been recorded and, by analogy to previous studies of furazan (1,2,5-oxadiazole) and 1,2,5-thiadiazole, an interpretation of the spectrum in terms of an allowed electronic transition involving primarily activity of ν5, a symmetric ring in-plane bending vibration, and ν10, a ring out-of-plane bending vibration, has been made. This analysis indicates that the excited state is non-planar, and the barrier to planarity has been calculated to be in the order of 115 cm−1.

ISSN:0008-4042    

DOI:10.1139/v74-014

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Dilute solutions of aliphatic thiols have been prepared and photolyzed at 253.7 nm in 3-methylpentane glasses at 77°K. The major products formed initially are thiyl radicals RS• and hydrogen atoms. Both of these are hot and yield solvent radicals by abstraction reactions, and relatively small amounts of RS2•, RS•, and possibly R1R2C=S. Thermal annealing of the matrices is accompanied by loss of hydrocarbon radicals through cage reactions and concommitant increase in the RS• concentration. An intermediate radical of the type R1R2ĊSH may also be produced in the annealing process. The photometric and spin resonance characteristics of RS•, RS2•and R1ĊH—SH are discussed and related to other systems in which these intermediates are observed. RS• is characterized in the amorphous phase by an absorption at 405 nm and a broad asymmetrical e.p.r. resonance nearRS2• has a non-axialg-tensor with principal values of about 2.06, 2.02, and 2.00 and has no detectable absorptions between 350 and 1200 nm.The photolytic behavior of these metastable radical species is also investigate

ISSN:0008-4042    

DOI:10.1139/v74-015

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The methyl 3,6-dideoxy-3-nitrohexopyranosides having the α-L-galacto(1), α-L-manno(2), α-L-galacto(3), and α-L-talo(4)configurations and their 2,4-diacetates (6, 11, 16, and18, respectively) served as starting materials for the preparation of 2,3- and 3,4-unsaturated derivatives. The reactions employed included dehydroacetylation of diacetates and of some monoacetates (5,7, and12) that had been obtained by partial acetylation or partial acid-catalyzed de-O-acetylation, and also dehydrations occurring under conditions of acetylation. The following nitroolefins were obtained: methyl 3,4,6-trideoxy-3-nitro-α-L-erythro-hex-3-enopyranoside (8) and its 2-acetate (9), the corresponding α-L-threoisomer (13) and its 2-acetate (10) and 2-O-methyl derivative (20), and methyl 2,3,6-trideoxy-3-nitro-α-L-erythro-hex-2-enopyranoside (14) and its 4-acetate (15) as well as the 4-acetate (17) of the corresponding α-L-threoisomer. In addition, 1,4-di-O-acetyl-2,3,6-trideoxy-3-nitro-α-L-threo-hex-2-enose (19) was obtained by acetolysis of17. Factors assumed to be responsible for a pronounced regioselectivity in some of the reactions are discussed.

ISSN:0008-4042    

DOI:10.1139/v74-016

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

L-Desosamine (3,4,6-trideoxy-3-dimethylamino-L-xylo-hexose), the enantiomer of a widely distributed antibiotics component, was synthesized by borohydride reduction of methyl 3,4,6-trideoxy-3-nitro-α-L-erythro-hex-3-enopyranoside followed by catalytic hydrogenation of the nitro group,N,N-dimethylation of the resulting saturated amino glycoside, and acid hydrolysis of the glycosidic bond.

ISSN:0008-4042    

DOI:10.1139/v74-017

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A new synthetic route of 4-(4-methyl-4-hydroxyamyl)-Δ3-cyclohexenecarboxaldehyde (Lyral) from myrcene (1) was investigated. It involves subjecting1first to the diene synthesis with acrolein (2) followed by hydration of the morpholine enamine of the adduct in 50% sulfuric acid at 0–5° and the subsequent hydrolysis in diluted sulfuric acid at 15–20°.The present method is superior in simplicity as well as productivity for the preparation of Lyral to any other methods hitherto reported.

ISSN:0008-4042    

DOI:10.1139/v74-018

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Treatment ofN-phenylisomaleimide with aziridine gave 3-(N′-aziridinyl)-N-phenylsuccinimide identical with the adduct formed betweenN-phenylmaleimide and ethylenimine. The isomerization proceeded through the intermediate2whose decomposition in solution to a mixture of3,4, and5is also described.

ISSN:0008-4042    

DOI:10.1139/v74-019

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The photocyclization–oxidation reaction of 1-phenyl-4-(2′-thienyl)-1,3-butadiene gave 4-phenyl-benzo[b]thiophene. Similarly, irradiation of 1-phenyl-4-(3′-thienyl)-l,3-butadiene gave 7-phenylbenzo-[b]thiophene. Thus, photocyclization occurs exclusively to the thiophene ring. Irradiation of 1,4-di(2′-thienyl)-1,3-butadiene and 1,4-di(3′-thienyl)-1,3-butadiene yielded 4-(2′-thienyl)benzo[b]thiophene and 7-(3′-thienyl)benzo[b]thiophene, respectively. Photocyclization of 1-(2′-thienyl)-4-(3″-thienyl)-1,3-butadiene gave an inseparable mixture of 4-(3′-thienyl)benzo[b]thiophene and 7-(2′-thienyl)benzo[b]thiophene.

ISSN:0008-4042    

DOI:10.1139/v74-020

出版商:NRC Research Press    

年代:1974

数据来源: NRC