The synthesis of 2-amino-4-aryl-3-ethoxycarbonyl-4H-naphtho[1,2-b]pyrans revisited

An expeditious and unequivocal synthesis of some 2-amino-4-aryl-3-ethoxycarbonyl-4H-naphtho-[1,2-b]pyrans 3 is reported. Previous papers describing the preparation of this type of compound have been amended and a convenient and direct procedure for its preparation is now presented.     

Synthesis and optical characterization of new ketocyanine dyes with extended polymethine chaines

New symmetrical and unsymmetrical near-infrared absorbing ketocyanine-type dyes are synthesized and their optical characterization is done. The relationships between their structure and optical properties are discussed. The synthesized ketocyanine dyes show a positive solvatochromism and are poorly fluorescent. A new procedure for the preparation of N,N,N′,N′-tetramethylvinamidinium perchlorate, which was a very useful reagent for the synthesis of various heterocyclic compounds as well as for the preparation of cyanine dyes is developed.     

A convenient preparation of 2-thioxo-4(3H)-quinazolinones

A simple method is described for the preparation of 3-aryl-2-thioxo-4(3H)-quinazolinones (4) by the reaction of anthranilic acids and ammonium or triethylammonium N-aryl-dithiocarbamates in ethanol. The method is also applicable to the preparation of 3-ethyl-2-thioxo-4(3H)-quinazolinone.     

Synthesis of Arenetricarbonylmanganese Cations and Hydrogen Migrations in the Cyclohexadienyltricarbonylmanaganese Series

Improvements in the preparation of some arenetricarbonylmanganese cations and the preparation of (1,4-dimethoxybenzene)tricarbonylmanganese hexafluorophosphate are described. Substitution of hydrocarbon groups into these complexes is possible via the known exo-addition of organolithium reagents followed by thermal hydrogen-shift and then hydride abstraction. The rearrangement is shown to involve migration of the 6-endo hydrogen probably via a metal-hydride intermediate.     

Thionyl Chloride–Mediated Synthesis of tert-Butyl ((S)-1-((R)-Oxiran-2-yl)-2-phenylethyl)carbamate with Boc-Involved Neighboring Group Participation

A convenient, high-yielding preparation of tert-butyl ((S)-1-((R)-oxiran-2-yl)-2-phenylethyl)carbamate is described. An efficient chiral inversion as the key step is furnished via Boc-involved neighboring group participation mediated by thionyl chloride. This preparation has significant advantages over the previously reported methods with respect to simplicity, cost efficiency, yield, and purification procedure as well as industry reliability.     

Improved Preparation of 1,3-Bis(2,6-di-iso-propylphenyl)imidazolium Tetrafluoroborate

A convenient, high-yielding, multi-hundred-gram preparation of 1,3-bis(2,6-di-iso-propylphenyl)imidazolium tetrafluoroborate is described. The preparation of this salt has significant advantages over the chloride as it eliminates potential bis(chloromethyl) ether formation. The improved conditions provided the tetrafluoroborate salt in 61% overall yield in two steps from 2,6-di-iso-propylaniline.     

Preparation of some tricyclic fused ring iminopyrido[3,2-e]pyrimidines

The preparation of a number of tricyclic fused ring iminopyrido[3,2-e]pyrimidines is described. Treatment of 2-chloronicotinonitrile with primary amines afforded the corresponding 2-amino derivative which was condensed with ethylenediamine or higher congeners to give substituted cyclic amidines. The latter on treatment with cyanogen bromide gave the desired imino-pyrido[3,2-e]pyrimidines. The preparation of diaminopyrido[2,3-d]pyrimidines and tricyclic quinazolines by related procedures is discussed.     

Enantioselective Nitrogen Transfer to Sulfides from Nitridomanganese(V) Complexes

We describe the facile preparation of novel, optically active nitridomanganese(V) complexes which serve as reagents for the electrophilic amination of sulfides. This amination method has several appealing features, including: i) the facile preparation of large quantities of the starting nitridomanganese reagent 3 , ii) the preparation of acylsulfilimines 2 in optically active form, and iii) the mild reaction conditions employed.     

Preparation and Properties of Novel Cationically Active Oligo-p-Methoxystyryl-Silica Composites

Abstract

The preparation of cationically active oligo-p-methoxystyrene-silica composites by cationic interfacial polymerization is described. In addition to the effective preparation of the interfacial initiator, p-methoxybenzylium-hydrogen sulfate-silica, and p-methoxybenzylium-trifluoroacetate-silica, a procedure to yield new kinds of composites is reported. The outstanding properties of the “living” oligo-p-methoxy-styryl-hydrogen sulfate-silica is demonstrated by means of zeta potential measurements, solid-state ¹³C-NMR spectroscopy, UV/Vis spectroscopy, and electron scanning microscopy.     

Preparation of pyrylium salts from 2-phenyl-5H-phenaleno [ 1,9-bc] pyran-5-one

The preparation of 2-phenyl-5H-phenaleno[ 1,9-bc]pyran-5-one ( 7 ) is described. Compound 7 undergoes reactions typical of pyrones and was therefore a useful intermediate for the preparation of pyrylium salts. Several pyrylium dyes were prepared from 7 and the long-wavelength absorptions of these dyes were compared with those of the corresponding flavylium dyes.     

Chemical profiling approach to evaluate the influence of traditional and simplified decoction methods on the holistic quality of Da‐Huang‐Xiao‐Shi decoction using high‐performance liquid chromatography coupled with diode‐array detection and time‐of‐flight mass spectrometry

Da‐Huang‐Xiao‐Shi decoction, consisting of Rheum officinale Baill, Mirabilitum, Phellodendron amurense Rupr. and Gardenia jasminoides Ellis, is a traditional Chinese medicine used for the treatment of jaundice. As described in “Jin Kui Yao Lue”, a traditional multistep decoction of Da‐Huang‐Xiao‐Shi decoction was required while simplified one‐step decoction was used in recent repsorts. To investigate the chemical difference between the decoctions obtained by the traditional and simplified preparations, a sensitive and reliable approach of high‐performance liquid chromatography coupled with diode‐array detection and electrospray ionization time‐of‐flight mass spectrometry was established. As a result, a total of 105 compounds were detected and identified. Analysis of the chromatogram profiles of the two decoctions showed that many compounds in the decoction of simplified preparation had changed obviously compared with those in traditional preparation. The changes of constituents would be bound to cause the differences in the therapeutic effects of the two decoctions. The present study demonstrated that certain preparation methods significantly affect the holistic quality of traditional Chinese medicines and the use of a suitable preparation method is crucial for these medicines to produce special clinical curative effect. This research results elucidated the scientific basis of traditional preparation methods in Chinese medicines.     

The Photophysics of Thin Polymer Films of Poly-(meta-phenylene-co-2,5-dioctoxy-para-phenylenevinylene)

Summary.  We have investigated the effect of film preparation procedures on the photoluminescence efficiency of the luminescent co-polymer poly-(m-phenylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV). The photoluminescence efficiency of PmPV films improved by up to 50% when the solution was degassed by bubbling argon gas through it prior to spin casting in an inert atmosphere and baking under vacuum. Photoinduced absorption and doping measurements show that this preparation method reduces polaron photogeneration, which reduces the photoluminescence (PL) yield through exciton quenching and excited state absorption. It is proposed that this sample preparation method increases interchain separation, reducing the formation of polarons and non-radiative quenching routes, thus resulting in increased PL efficiency. Received June 23, 2000. Accepted (revised) August 3, 2000     

Stereoselective Syntheses of Tetrahydroesterastin-β -Lactam Analogues

A total synthesis of the optically active tetrahydroesterastin β -lactam analogue 2 using Miller's hydroxamate approach is described (Scheme 2). Significant modification of published procedures has resulted in a short and facile stereospecific preparation of the N-[(benzyloxycarbonyl)methyl]-β -lactam 17 starting from the readily available D -serine. This material served as intermediate for the preparation of a variety of N-[(benzyloxycarbonyl)methyl]tetrahydroesterastin β-lactam analogues (Scheme 5).     

Synthesis of chromones

A general procedure for the preparation of chromones from the boron difluoride complex of o-hydroxyaryl methyl ketones is described. One of the best methods used for the preparation of chromones and benzochromones is the treatment of o-hydroxyaryl methyl ketones with the dimethylacetal of dimethylformamide followed by treatment with sulfuric acid (1). We previously had shown (2) that benzochromone 4 was prepared in reasonable yield by the following reaction sequence.     

Olefin Cross‐Metathesis: A Powerful Tool for Constructing Vaccines Composed of Multimeric Antigens

The preparation of biologically pertinent glycosylamino acids from O‐pentenyl glycosides is described. The procedure involves sequential cross‐metathesis reactions followed by hydrogenation. The generality and value of this procedure have been demonstrated by the preparation of peracetylated Gb3, GM2, and fucosyl GM1 glycosylamino acids, which are of potentially large value in the preparation of future anticancer vaccines.     

A New Preparation of 1,3,3‐Trimethylbicyclo[2.2.2]octan‐2,6‐dione,a Never Isolated Intermediate in a Total Synthesis of (+)‐Norpatchoulenol. Formal Total Synthesis of (±)‐Iso‐Norpatchoulenol

A new preparation and the isolation and spectroscopic characterization of 1,3,3‐trimethylbicyclo[2.2.2]octan‐2,6‐dione ( 3 ), a so far elusive key intermediate in the Liu–Ralitsch total synthesis of (+)‐norpatchoulenol ((+)‐ 1a ), is described. The preparation of 3 constitutes also a formal total synthesis of (±)‐iso‐norpatchoulenol ((±)‐ 1b ), since 3 is correlated to an intermediate in the Monti and co‐workers synthesis of (±)‐ 1b .     

Synthesis ofN-phenyl-substituted derivatives of morphine alkaloids

A method for the preparation ofN-phenyl-substituted morphine alkaloids by treatment of the correspondingN-nor derivatives with Ph₃Bi in the presence of Cu(OAc)₂ is proposed. 17-Nor-17-phenylthebaine thus obtained can serve as a convenient starting material for the preparation of otherN-phenyl-substituted alkaloids. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 595–598, March, 1999.     

Preparation of N,N'-bis-tert-Butoxycarbonylthiourea

The preparation of N,N'-bis-tert-butoxycarbonylthiourea from thiourea and di-tert-butyl dicarbonate in tetrahydrofuran is described.     

Synthesis and structure of (carboxymethyl)-functionalized cyclobuta-fused uracil dimers

Herein, we report a convenient method for the preparation of four benzyl-ester-protected, (carboxymethyl)-functionalized cyclobuta-fused uracil dimers 1–4 , including the desired cis-cisoid-cis,syn- configured isomer 1 , a compound which is suitable for the preparation of catalytic antibodies, synthetic receptors, and model compounds, required for the investigation of the DNA-lesion, recognition step and DNA-repair mechanisms. A comprehensive structure determination of each isomer by ¹H-NMR, and in the case of the cis-cisoid-cis,syn- and the cis-traftsoid-cis,Syn-dimers by X-ray crystal-structure analysis, is also provided.     

Pyridinethiones. IX preparation of ricinidine,thioricinidine and other 2(1H)-pyridones and -thiones related to nicotinic acid

2(1H)-Pyridones and -thiones related to 1-substituted nicotinic acid derivatives have been prepared via the corresponding l-substituted-3-formyl-2(1H)-pyridones and -thiones. A number of synthetic procedures for the interconversion of functional groups in these nicotinic acid derivatives are given i.e. preparation of the aldoximes, nitriles, carboxamides and carboxylic acids as well as the 3- hydroxyalkyl derivatives. The course of the basic peroxide oxidation of the l-substituted-3-formyl-2(1H)-pyridinethiones is found to be very dependent upon the electronegativity of the 1-substituent. A preparation of ricinidine is also described.