Synthesis of β-(9-purinyl)alanines

The corresponding 1-(6-substituted-9-purinyl)-2,2-diethoxyethanes were obtained by alkylation of 6-substituted purines with 1-bromo-2,2-diethoxyethane. Subsequent transformations of a large portion of the acetals gave 2-(6-substituted-9-purinyl) acetaldehydes, from which -(6-substituted-9-purinyl)alanines were obtained by the cyanohydrin synthesis. The classification of the compounds as N(₉)-substituted purine derivatives was proved by means of UV spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1561–1566, November, 1972.     

COPPER-CATALYSED REARRANGEMENT OF 4-SUBSTITUTED-2,3-1H-BENZOXAZINE-1-THIONES

Abstract

4-Substituted-2,3-1H-benzoxazine-1-thiones were prepared by the treatment of the corresponding benzoxazine-1-ones with P₂S₅. The thermal rearrangement of 4-substituted-2.3-1H-benzoxazine-1-thiones, catalysed by metallic copper, yielded 4-substituted-2.3-1 H-benzthiazine-1-ones.     

Synthesis of heterocyclics via enamines—IX : Reactions of 1-substituted-4,4,6-trimethyl-1,4-dihydropyrimidine-2(3h)thione derivatives with dihalocarbenes

Dichloroarbene with 1-substituted 4,4,6 trimethyl- 1,4 dihydropyrimidine 2(3H) thione derivatives (2) formed 7,7-dichloro 3 [(dichloromethyl)thio]-2-substituted-1,5,5-trimethyl-2,4-diazabicyclo[4,1.0] hept-3-ene (3) and 7,7-dichloro-2-substituted-1,5,5-trimethyl-2,4-diazabicyclo [4.1.0] heptane-3 thione (4). On heating as such or under acidic or basic conditions, 3 changed to the corresponding 4 quantitatively. Diiodocarbene with 2 (RCH₃, Ph) formed mainly the corresponding 1-substituted 4,4,6-trimethyl-1,4-dihydropyrimidine-2 one 7 (RCH₃ Ph) 7 (RCH₃).     

A Theoretical Study on the Tautomerism of C-Carboxylic and Methoxycarbonyl Substituted Azoles

DFT calculations (B3LYP/6-31+G^**) have been carried out on 106 tautomers and conformers of NH-azoles bearing CO₂H and CO₂CH₃ groups. The following azoles systems have been studied: 2-substituted pyrroles, 2-substituted indoles, 2-substituted imidazoles, 2-substituted benzimidazoles, 4(5)-substituted imidazoles, 3(5)-substituted pyrazoles, 3-substituted indazoles (1H and 2H), 3,4(5)-substituted-1,2,3(5)-triazoles, 2,3(5)-substituted-1,2(3),4-triazoles, 4(5)-1,2,3,4(5)-tetrazoles. In the case of pyrazole, 3,5-disubstituted derivatives have also been computed, including four dimers.Dedicated to our friend Professor Vladimir I. Minkin on his 70th anniversary.     

Microwave-mediated synthesis and manipulation of a 2-substituted-5-aminooxazole-4-carbonitrile library

A 2-substituted-5-aminooxazole-4-carbonitrile library has been synthesised and modified via microwave-mediated and flow chemistries. One synthesised compound, 5-(1H-pyrrol-1-yl)-4-(1H-tetrazol-5-yl)-2-(thien-2-yl)oxazole, contains three distinct heterocycles attached to the central oxazole core, highlighting the structural diversity of this approach. Three oxazoles had micromolar k_i values against cannabinoid (CB1/CB2) receptors.     

Iridium complex-catalyzed allylic amination of allylic esters

Iridium complex-catalyzed allylic amination of allylic carbonates was studied. The solvent strongly affected the catalytic activity. The use of a polar solvent such as EtOH is essential for obtaining the products in high yield. The reaction of (E)-3-substituted-2-propenyl carbonate and 1-substituted-2-propenyl carbonate with pyrrolidine in the presence of a catalytic amount of [Ir(COD)Cl](2) and P(OPh)(3) (P/Ir = 2) gave a branch amine with up to 99% selectivity. Both secondary and primary amines could be used for this reaction. When a primary amine was used, selective monoallylation occurred. No diallylation product was obtained. The reaction of 1,1-disubstituted-2-propenyl acetate with amines exclusively gave an alpha,alpha-disubstituted allylic amine. This reaction provides an alternative route to the addition of an organometallic reagent to ketimines for the preparation of such amines. The reaction of (Z)-3-substituted-2-propenyl carbonate with amines gave (Z)-linear amines with up to 100% selectivity. In all cases, no (E)-linear amine was obtained. The selectivities described here have not been achieved in similar palladium complex-catalyzed reactions.     

Synthesis of novel 1-alkyl or 1-aryl-2-(4-substituted-1-piperazinyl)-1-H-benzothieno[2,3-d]imidazoles

The synthesis of novel 1-alkyl or 1-aryl-2-(4-substituted-1-piperazinyl)-1-H-benzothieno[2,3-d]imidazoles 7e-x starting from 2-nitro-3-bromobenzo[b]thiophene is described. These compounds were prepared as potential H₁-antihistaminic agents.     

An efficient one pot–three component cyclocondensation in the synthesis of 2-(2-chloroquinolin-3-yl)-2,3-dihydroquinazolin-4(1H)-ones: potential antitumor agents

Montmorillonite K10 efficiently catalyzed a one pot–three component cyclocondensation of isatoic anhydride, NH₄OAc and aromatic/heteroaromatic aldehydes under ambient conditions to produce the corresponding 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in good yields. The 2-(2-chloroquinolin-3-yl)-2,3-dihydroquinazolin-4(1H)-ones 3a–d were screened for their antitumor activity against Ehrlich Ascites Carcinoma tumor cells     

Steric redirection of alkylation in 1H-pyrazole-3-carboxylate esters

The alkylation of ethyl 1H-pyrazole-3-carboxylate with a variety of alkylating agents in the presence of K₂CO₃ was found to largely favor the formation of ethyl 1-substituted pyrazole-3-carboxylates. The alkylation could be sterically redirected by the use of a triphenylsilyl group (ethyl 3-(triphenylsilyl)-1H-pyrazole-5-carboxylate) to provide synthetically useful yields of ethyl 1-substituted-3-(triphenylsilyl)-1H-pyrazole-5-carboxylates. The triphenylsilyl group could be removed with Bu₄NF. Other triorganosilyl groups (TMS, TES, TBDMS) failed to provide significant redirection, while TIPS proved refractory to protodesilylation.     

含脱羧脱氢松香基的1,2,4-三唑并[3,4-b]-1,3,4-噻二唑衍生物的合成、表征及抑菌活性

用POCl3为催化剂和脱水剂,3-取代-4-氨基-5-巯基-1,2,4-三唑4和10分别与脱氢松香酸1反应制得14种未见文献报道的3-取代-6-(4′-脱羧脱氢松香基)-1,2,4-三唑并[3,4-b-]-1,3,4-噻二唑衍生物]5a~5e和11a~11i;所有化合物的结构均经IR、¹H NMR、¹³C NMR 和MS测试技术分析确认。 抑菌活性测试表明,目标化合物对白色念珠菌(C.Albicans)、大肠杆菌(E.Coli)、藤黄微球菌(M.Luteus)和痢疾志贺杆菌(S.Dysenteriae)均有一定的抑制作用。     

4-Substituted-3-alkyl-3,4-dihydro-2H-1,3-benzoxazin-2-ones II (1,2). Solvolytic transformations of urea and thiourea derivatives into 1-alkyldihydro-6-(2-hydroxyaryl)-1,3,5-triazine-2,4-(1H,3H) diones

A series of 3,4-Dihydro-2-oxo-(3-substituted-2H-1,3-benzoxazin-4-yl)ureas (II, Table I) and 3,4-dihydro-2-oxo-(3-substituted-2H-1,3-benzoxazin-4-yl)thioureas (Table II) was prepared by treating 3,4-dihydro-4-hydroxy-3-substituted-2H-1,3-benzoxazin-2-ones with ureas and thioureas, respectively. In the presence of alcoholic alkali these compounds underwent transacylation to dihydro-6-(2-hydroxyaryl)-1,3,5-triazine-2,4-(1H,2H)diones (Table III) and their 4-thio analogues (Table IV).     

Intramolecular SN2 reaction α- to a trifluoromethyl group: preparation of 1-cyano-2-trifluoromethylcyclopropane

The first intramolecular S_N2 reaction of α-trifluoromethylated secondary alcohols by a carbanion is described. A stereoselective intramolecular cyclization of 3-substituted-3-cyano-1-trifluoromethylpropyl sulfonate via the cyano stabilized carbanion provides 1-substituted-1-cyano-2-trifluoromethylcyclopropanes in good yields. The product has the opposite configuration to the starting alcohol at the carbon attached to trifluoromethyl group, revealing the reaction takes place in S_N2 manner with Walden inversion at the reaction center.     

Synthesis and mass spectral studies of 1-[5-chloro-1-substituted-2(1H)-pyrazin-2-on-3-yl]-5-aryl-3-methylpyrazoles

Sixteen new 1-[5-chloro-1-substituted-2(1H)-pyrazin-2-on-3-yl]-5-aryl-3-methylpyrazoles V have been synthesized by condensation of 5-chloro-1-substituted-3-hydrazino-2(1H)-pyrazin-2-ones III and 1-aryl-1,3-butanediones IV in dry 1,4-dioxane. The general mass spectral fragmentation mode of these compounds has been studied.     

Halogen effects in Robinson-Gabriel type reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh3/CX4

We found that the reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh₃/CCl₄ proceeded smoothly to give the corresponding normal Robinson-Gabriel type product 2-cyclopropyl-5-substituted-[1,3,4]-oxadiazoles in good yields. Using CBr₄ or CI₄ instead of CCl₄ in the above system, the ring opening of cyclopropane occurred after dehydration to give the corresponding 2-(3-halopropyl)-5-substituted-[1,3,4]-oxadiazoles (4 or 5) in good yields.     

Synthesis of optically active α-(allenyl)- and α-substituted-α-(allenyl)glycines

The synthesis of various types of optically active α-(allenylsilane-containing)glycines via a chirality-transferring ester-enolate Claisen rearrangement of α-acyloxy-α-alkynylsilanes is described. The conversion of the rearranged products into the optically active silicon-free α-(allenyl)- and α-substituted-α-(allenyl)glycines was achieved by the removal of the Me₂PhSi- or TMS group from the allene terminus.     

新型3-取代-6-(4-氯苯基)-7-(1H-1,2,4-三唑-1-基)-1',2',4'-三唑[3,4-b]-1",3",4"-噻二嗪衍生物的合成及抗菌活性

通过3-取代-4-氨基-5-巯基-1,2,4-三唑(3a～3m)和2-溴-2-(1H–1,2,4-三唑-1-基)-4′-氯代苯乙酮(2)的缩合反应, 合成了13个新型3-取代-6-(4-氯苯基)-7-(1H-1,2,4-三唑-1-基)-1',2',4'-三唑[3,4-b]-1",3",4"-噻二嗪衍生物4a～4m. 化合物结构经元素分析, ¹H NMR, IR和MS进行了表征. 抗菌试验表明所合成的化合物对细菌表现出中等程度的抑制活性.     

Mass spectra of some 1-(6′-substituted-4′-methyl-2′-quinolyl)-3-methylpyrazol-5-ols and their 4-substituted analogues

Electron impact induced fragmentation of some 1-(6′-substituted-4′-metbyI-2′-quinolyI)-3-methylpyrazoI-5-ols follows a route where the pyrazole moiety is preferentially cleaved with successive losses of two moieties of 41 u. High-resolution measurements have established that the first loss is due to the ?₂HO moiety, which necessitates an intramolecular hydrogen transfer followed by ring fission. The resultant ion loses CH₃CN in a subsequent step. The origin of many fragment ions was traced with the use of B/E linked-scan spectra.     

Synthesis of novel heterocycles from thiazolecarbohydrazides

Cyclization of 2-methyl (or -phenyl)-5-phenylthiazole-4-carbohydrazides (1) and (2) under various conditions gives differing oxadiazoles: 2-(2-substituted-5-phenyl-4-thiazolyl)-1,3,4-oxadiazole-5-thiones (7) and (8), and 2-(2-substituted-5-phenyl-4-thiazolyl)-1,3,4-oxadiazoles (9) and (10). Cyclodehydration of thiazolecarbonyl-thiosemicarbazides (3)–(6) with NaOH givesthe 3-(2-substituted-5-phenyl-4-thiazolyl)-4-substituted-4H-5-mercapto-1,2,4-triazoles (11)–(14), while H ₃ PO ₄ gives the 2-(2-substituted-5-phenyl-4-thiazolyl)-5-phenylamino-1,3,4-thiadiazoles (15) and (16).A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 679–683, March, 1992.     

Synthesis of 4-hydroxy-3-[(E)-2-(6-substituted-9H-purin-9-yl)vinyl]coumarins as lipoxygenase inhibitors

The synthesis of 4-hydroxy-3-[(E)-2-(6-substituted-9H-purin-9-yl)vinyl] coumarins has been achieved from the reactions of 4-hydroxycoumarin with 2-(6-substituted-9H-purin-9-yl)acetaldehydes in DMF under heating. The new compounds showed significant lipoxygenase inhibitory activity (e.g., 6a: IC₅₀ = 6.25 μM).     

The origin and nature of the π-electron steric effect

The existence of conformational or steric proximity substituent effects involving π-electrons has been demonstrated in a number of recent reports but the question of whether this effect is due simply to the size of the substituent or to lone pair electrons on the substituent has not been investigated. Relative to this question, pK_a's for an extensive series of 2'- and 4'-substituted-4-aminobiphenyls and for a series of 4'-substituted-2-amino-biphenyls have been determined. The results of this study demonstrate that a π-electron steric effect is operative in the 2'-substituted-4-aminobiphenyls and that it occurs primarily (when possible) via lone pair electron-π electron interactions and not simply via a steric size effect. The pK_a data for the 4'-substituted-2-aminobiphenyls reinforce this conclusion and further demonstrate that 2,4'-resonance is possible in appropriately substituted 2,4'-disubstituted biphenyls. In addition, the relativity of the concept of substituent size and of electron withdrawing or donating character of various groups is illustrated.