Studies on the esterifications of 9-（hydroxyimino）-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one with acid chlorides under different conditions

The esterifications of 9-（hydroxyimino）-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one （4） with acid chlorides afforded normal oxime-esters 3a-e in 35-78% yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger, whereas the reactions gave unexpected 8-substituted products N-（8-chloro-4-methyl-2-oxo-2H-furo-[2,3-h]chromen-9-yl）amides （5a-c） and 4-methyl-2,9-dioxo-8,9-dihydro-2H-furo[2,3-h]chromen-8-ylcarboxyloates （6d-e） by using excessive acid chlorides. The structures of 10 new compounds were determined by 1H NMR, 13C NMR, MS and HRMS, and the possible mechanism for the formation of unexpected products 5a--c and 6d-e was also proposed.     

Fluorescent sensing of anions based on excited state intramolecular proton transfer in N-(3-hydroxy-2- naphthamido)-N′-phenylthiourea

A neutral N-amidothiourea-based excited state intramolecular proton transfer (ESIPT) anion receptor bearing an o-hydroxynaphthamide fluorophore and a thiourea binding site, N-(3-hydroxy-2-naphthamide)-N’-phenylthiourea (1a), was designed and synthesized. Fluorescence and absorption response of 1a toward anions were assessed in acetonitrile. IR and NMR experiments indicated that the "OH…O=C" intramolecular hydrogen bond (IHB) in 1a was weak so that it only exhibited the short-wavelength normal emission other...     

The invalidity of intermolecular proton transfer triggered twisted intramolecular charge transfer in excited state for 2-(4′-diethylamino-2′-hydroxyphenyl)-1H-imidazo-[4,5-b]pyridine

The excited-state dynamics of the excited-state proton transfer and intramolecular twisted charge transfer (TICT) reactions of a molecular photoswitch 2-(4′-diethylamino-2′-hydroxyphenyl)-1H-imidazo-[4,5-b]pyridine (DHP) in aprotic and alcoholic solvents have been theoretically investigated by using time-dependent density functional theory. The excited-state intramolecular proton transfer (ESIPT) reaction of DHP proceeding upon excitation in all the solvents has been confirmed, and the dual emission has been assigned to the enol and keto forms of DHP. However, for methanol and ethanol solvents within strong hydrogen-bonded capacity, the intermolecular hydrogen bonds between DHP and methanol/ethanol would promote an excited-state double proton transfer (ESDPT) along the hydrogen-bonded bridge. Importantly, the previous proposed ESDPT-triggered TICT mechanism of DHP in methanol and ethanol was not supported by our calculations. The twist motion would increase the total energy of the system for both the products of ESIPT and ESDPT. According to the calculations of the transition states, the ESDPT reaction occurs much easier in keto form generated by ESIPT. Therefore, a sequential ESIPT and ESDPT mechanism of DHP in methanol and ethanol has been reasonably proposed.     

A Fast Assembly of （-）-Epigallocatechin-3-gallate [（-）-EGCG] via Intra- and Inter-molecular Mitsunobu Reaction

This paper described a concise construction of （-）-EGCG （1f） （with an overall yield of 20% for seven steps based on the starting cinnamyl alcohol derivative 3）, featuring asymmetric dihydroxylation （ADH）, intra- and inter-molecular Mitsunobu reaction as key steps. Our strategy disclosed herein constitutes a new effective general synthetic approach toward the analogues of （-）-EGCG （1f）.     

Synthesis and characterization of α-{ 3-[2-hydroxy-3- （N-methyl-N-hydroxy-ethylamino）propoxy]propyl}-ω- butylpolydimethylsiloxanes

α-{ 3-[2-hydroxy-3-（N-methyl-N-hydroxyethylamino）propoxy]propyl }-α-butylpolydimethylsiloxanes III with various molecu- lar weights were prepared by epoxy addition of α-[3-（2,3-epoxy-propoxy）propyl]-α-butylpolydimethylsiloxanes Ⅱ and N- methylmonoethanolamine. At each step, the outcome compounds were characterized through FT-IR and NMR spectra, the results showed that each step was successfully carried out and objective products were achieved.     

Synthesis and Crystal Structure of Ethyl（2-amino-4-（3-nitrophenyl）-1,4-dihydro-2H-pyrano[3,2-h]quinolin-3-）carboxylate

1 INTRODUCTION 2-Aminochromene is an important class of com- pounds found as the main compounds of many naturally occurring products employed as cos- metics and pigments[1] and utilized as potential biodegradable agrochemicals[2～4]. The utility of fluoride salts as potential base in variety of syn- thetic reactions has been recognized in recent years[5, 6]. However, low solubility of fluoride salts in ordinary solvents limits their wide applications in organic syntheses. On the other ha…     

Synthesis and Crystal Structure of 1-（4-Bromobenzoyl）-3- [5-（E）-styryl-1,3,4-thiadiazol-2-yl]urea

1 INTRODUCTION 1,3,4-Thiadiazole derivatives represent an interes- ting class of compounds possessing broad spectrum biological activities[1~4]. Aroyl ureas are known to exhibit diverse biological effects, such as insecticidal, fungicidal, herbicidal and plant growth regulating activities[5~8]. Therefore, it is worthwhile to investi- gate the compounds incorporating both 1,3,4-thiadia- zole nucleus and aroyl urea group. In the previous paper[9], a series of aroyl ureas containing 1,3,4-t…     

Chemoselective Dehydrogenation of 3-[2-（3,4-Dihydro-1-naphthalenyl）ethyl]imidazolidine-2,4-diones： a New and Convenient Synthesis of 13,16-Diazaequilenin analogs

The synthesis of the title compounds starting with the chemoselective dehydrogenation of 3-[2-(3,4-dihydro-1-naphthalenyl)ethyl]imidazolidine-2,4-diones has been described.     

Modified Coumarins. I. Synthesis of 5-Phenyl-7H-furo[2, 3-g]chromen-7-ones and 9-Phenyl-7H-furo-[2, 3-f]chromen-7-ones

5-Phenyl-7H-furo[2,3-g]chromen-7-ones and 9-phenyl-7H-furo-[2,3-f]chromen-7-ones, new analogs of psoralen and allopsoralen, are synthesized from 7-hydroxy- and 5-hydroxy-4-phenylcoumarins     

Modified Coumarins. 8. Synthesis of Substituted 5-(4-Methoxyphenyl)-7H-furo[3,2-g]chromen-7-ones

The MacLeod method was used to synthesize a series of substituted 5-(4-methoxyphenyl)-7H-furo[3,2- g]chromen-7-ones, modified analogs of psoralen, from 7-hydroxy-4-(4-methoxyphenyl)coumarins.     

Synthesis of 4-Hydroxy-3-(1-aryl-2-acetylethyl)-7,8-diaryl-2H-thieno(3,2-h)chromen-2-ones Using Cerium(III) Chloride

A new series of 4-hydroxy-3-(1-aryl-2-acetylethyl)-7,8-diaryl-2H-thieno(3,2-h)chromen-2-ones were synthesized in good yields by reacting 4-hydroxy-7,8-diaryl-2H-thieno(3,2-h)chromen-2-ones with various α,β-unsaturated ketones in presence of cerium(III) chloride in acetonitrile.     

Thiochromenone-Annelated Heterocycles: Regioselective Synthesis of Furo[3,2-b]-thiochromen-9-ones

Summary.  A number of hitherto unreported furo[3,2-b]thiochromenone derivatives were regioselectively synthesized in good yields starting from 3-allyloxy-thiochromenones. Received September 18, 2000. Accepted (revised) November 15, 2000     

Heteroannulated Quinazoline and Quinazolinone Derivatives from (Z)-2-[1-Benzamido-2-(3,4,5-trimethoxyphenyl)]vinyl-3,1-benzoxazin-4(3H)-one

The title compound 1 was prepared and allowed to react with a series of nitrogen nucleophiles to afford the quinazoline and quinazolinone derivatives 2–12 and tetrazole derivative 13. The IR, ¹H NMR, ¹³C NMR, and mass spectra of all the synthesized compounds were discussed.     

Synthesis,Characterization and In Vitro Evaluation of Novel 5-Ene-thiazolo[3,2-b][1,2,4]triazole-6(5H)-ones as Possible Anticancer Agents

The present paper is devoted to the search for drug-like molecules with anticancer properties using the thiazolo[3,2-b][1,2,4]triazole-6-one scaffold. A series of 24 novel thiazolo-[3,2-b][1,2,4]triazole-6-ones with 5-aryl(heteryl)idene- and 5-aminomethylidene-moieties has been synthesized employing three-component and three-stage synthetic protocols. A mixture of Z/E-isomers was obtained in solution for the synthesized 5-aminomethylidene-thiazolo[3,2-b]-[1,2,4]triazole-6-ones. The compounds have been studied for their antitumor activity in the NCI 60 lines screen. Some compounds present excellent anticancer properties at 10 μM. Derivatives 2h and 2i were the most active against cancer cell lines without causing toxicity to normal somatic (HEK293) cells. A preliminary SAR study had been performed for the synthesized compounds.     

Structure and Spectroscopic Studies of 4,8-bis(2-Hydroxybenzyl)-cis-octahydro[1,4]-oxazino [3,2-b]-1,4-oxazine

The title compound 4,8-bis(2-Hydroxybenzyl)-cis-octahydro [1,4]-oxazino [3,2-b]-1,4-oxazine (1) has been synthesized by the reaction of N-(2-hydroxybenzyl)-2-amino-1-ethanol with glyoxal. This novel compound was characterized by elemental analysis, IR, and ¹H NMR. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic C2/C space group with unit cell dimensions: a = 18.318(4), b = 8.6110(17), c = 13.267(3) Å, = 119.90(3), V = 1814.1(6) ų, Z = 4. The two fused six-membered rings in 1 adopt chairlike conformations slightly flattened around the nitrogen atoms. In the central fusion bond, the geometry is a staggered conformation, with the two angular hydrogen atoms in the cis positions with respect to the rings, the nitrogen atoms antiperiplanar to each other, while the oxygen atoms remain gauche to each other and antiperiplanar to the hydrogen atoms. The ring conformations in 1 have been discussed on the basis of the anomeric effects and the presence of two strong intramolecular hydrogen bonds between the phenolic hydrogens and the amino groups.     

Accessing Dihydropyrrolo[3,4-b]indol-1(2H)-ones via Pd-Catalyzed Intramolecular Aminocarbonylative Ring Closure

Present in a number of small molecule derivatives that display a wide range of biological activities, the dihydropyrrolo[3,4-b]indol-(2H)-one (DHPI) core represents an underexplored heterocyclic scaffold. Given the pharmaceutical potential of the DHPI motif, the development of synthetic methodologies that permit their expedient assembly would be highly desirable. Herein, we describe a novel strategy for the construction of the DHPI core from 3-iodo-1H-indolyl substrates, employing an unprecedented Pd-catalyzed intramolecular aminocarbonylative ring closure. The compatibility of our optimized protocol with various functional groups is highlighted through the synthesis of a range of diversely substituted DHPI derivatives in up to 90 % isolated yield.     

Synthesis and Crystal Structure of (E)-Ethyl (9-bromo-5-oxo-4-phenyl-1,10b-dihydro-5H-pyrano [3,4-c] chromen-2-ylidene) Acetate

The crystal structure of the title compound (C22H17BrO5 , Mr = 441.27) has been determined by single-crystal X-ray diffraction. The crystal is of orthorhombic system, space group Pna21 with a = 11.76(1), b = 14.58(1), c = 11.52(1), V = 1973.93 , Z = 4, Dc = 1.485 g/cm3 , F(000) = 896, μ(MoKα) = 2.113 mm-1 , the final R = 0.0394 and wR = 0.0809 for 3918 observed reflections (Ⅰ > 2 (Ⅰ)). The single-crystal X-ray diffraction data indicate that the C=C bond is in an E-configuration. The intramolecular C(10)-H(10B)···O(4) and intermolecular C(17)-H(17)···O(4) hydrogen bonds contribute to the stability of the structure.