Reactivity of 3-cyano-1-methylpyridinium iodide in aqueous ammonia or amine solutions

Reaction of 3-cyano-1-methylpyridinium iodide (1) with aqueous methylamine or ethylamine yields 1-alkyl-3-alkyliminomethyl-2-imino-1,2-dihydropyridines 8. The related aldehydes 9 on alkaline treatment give 2-alkylamino-3-pyridinecarbaldehydes 10. Experimental evidence, including the related reactions of 1 with aqueous ammonia and diethylamine as well, suggest a general reaction sequence initiated by the attack of the nucleophile, followed by ring-opening, transamination and ring-closing steps.     

β-Lactam Templated Macrocyclization： Synthesis of 12-Membered Macrolide

A novel macrolactonization method was developed using a chiral β-lactam as the template. This novel method features that the macrocyclization is simultaneously achieved while a TBS protected hydroxy group is deprotected.     

2-Chloro-1-methylpyridinium iodide,an efficient reagent for the conversion of alcohols into alkyl thiocyanates both under solvent and solvent-free conditions

A new application of the Mukaiyama reagent for the simple phosphine-free conversion of alcohols into the corresponding alkyl thiocyanates is described. This transformation can be achieved either in acetonitrile or under solvent-free conditions and the products obtained in good to excellent yields. The solvent-free procedure described here is the first report on the solvent-free thiocyanation of alcohols.     

A novel route to synthesize libraries of quinoxalines via Petasis methodology in two synthetic operations

This Letter reveals an innovative and facile procedure to prepare quinoxalines in two synthetic steps. The microwave assisted Petasis reaction is followed by the acid mediated unmasking of an internal amino nucleophile, cyclodehydration and oxidation to give collections of quinoxalines in good to excellent yields.     

Isomerization of thiocarboxylic esters of 1-bromo-2-propanol and 2-bromo-1-propanol

Conclusions The rate constant for the isomerization of the thioacetates and thiobenzoates of l-bromo-2-propanol and 2-bromo-1-propanol in aprotic solvents, in contrast to the case for the esters of the corresponding carboxylic acids, is independent of the nature of the group adjacent to the thiocarboxylic group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1418–1420, June, 1988.     

A convenient synthetic route to a useful synthon: 4-bromo-2-pyridinecarboxaldehyde

We have developed a novel four-step method to synthesise 4-bromo-2-pyridinecarboxaldehyde, from 2-picoline-N-oxide via 4-nitro-2-pyridinecarboxaldehyde, under mild reaction conditions.     

Rotational isomerism. A gas-phase 1H nuclear magnetic resonance study of 1-bromo-2-chloroethane

The average vicinal coupling constants of 1-bromo-2-chloroethane at different temperatures have been obtained in a gas-phase ¹H NMR study of 1,2-disubstituted ethanes. Analysis of the experimental data, assuming a ”static” model with constant values for the vicinal coupling constants of the individual rotamers, yielded unacceptable results. A ”dynamic” model, which takes into account the torsional vibrations, has therefore been developed and used to analyse the gas-phase results. The values at 305 K for the vicinal coupling constants of the individual rotamers are: trans rotamer J_T = 13.6 Hz, J'_t = 4.9 Hz; gauche rotamer $\text{1}\text{2}$(J_G1 + J_G2) = 0.9 Hz, $\text{1}\text{2}$(J'_G1 + J'_G2) = 7.8 Hz. These couplings are temperature-dependent with J_T changing about four times as much as the other coupling constants. Analysis of the average vicinal coupling constants, measured in different solvents, with the “dynamic” model gave values for the vicinal coupling constants of the individual rotamers in excellent agreement with those from the gas-phase data. The value of $\text{1}\text{2}$(J_G1+ J_G2) decreases noticeably with increasing dielectric constant of the solution. This can be explained by changes in the average dihedral angle between the coupling protons, in the gauche rotamers, which leads to changes of J_G1 and J_G2 in the same direction.     

Determination of cysteine in human plasma by high-performance liquid chromatography and ultraviolet detection after pre-column derivatization with 2-chloro-1-methylpyridinium iodide

This paper describes the development and validation of a reversed-phase HPLC method with isocratic conditions for the analysis of total cysteine in human plasma. The essential steps in the assay include derivatization of cysteine via thiol group with 2-chloro-1-methylpyridinium iodide (CMPI), separation of the formed cysteine S-pyridinium derivative from endogenous thiol derivatives, usually present in biological samples, by ion-pair reversed-phase HPLC, and ultraviolet detection. Free cystine and protein-bound cysteine are converted to their reduced counterpart by the use of 2-mercaptoethanol. The standard curve is linear over the concentration range from 20 to 300 nmol ml(-1). The recoveries are from 93.9 to 105.9% and imprecision was at most 2.5%. Optimal conditions are determined for all steps of the analytical procedure.     

Synthesis and characterization of 5-bromo-3-sec-butyl-6-methyluracil

A new synthetic method for 5-bromo-3-sec-butyl-6-methyluracil (Bromacil) using 2-bromobutane and urea as starting materials is described. The synthesis involved condensation, cyclization and bromination with a total yield of 60%. The structure of Bromacil was determined by ¹H NMR, ¹³C NMR and IR spectroscopy. __________ Translated from Journal of Shandong University (Natural Science Edition), 2007, 42(7): 9–12 [译自: 山东大学学报(自然科学版)]     

1-bromo-1-lithioethene: a practical reagent for the efficient preparation of 2-bromo-1-alken-3-ols

A reliable preparative-scale synthesis of 1-bromo-1-lithioethene is reported. This reagent undergoes clean 1,2-addition with a range of aldehydes and ketones at -105 degrees C to afford the corresponding 2-bromo-1-alken-3-ols in moderate to excellent yield. Efficient diastereoselective addition to alpha-siloxy and alpha-methylcyclohexanones, as well as protected 3-keto furanose sugars, is achieved in the presence of 10 mol % CeBr(3). The resulting bromoallylic alcohol adducts have considerable potential as synthetic building blocks. [reaction: see text]     

Pyridinium ion reactivities: substituent effect on the reverse menschutkin reaction of 1-methylpyridinium cations with iodide anion

Substituent effect on the reverse Menschutkin reaction of 1-methylpyridinium cations with iodide anion can be described in terms of the LArSR equation with ?=3.60 which provides evidence against very late transition state of the nitrogen-to-iodine transmethylation.     

Chemical radiation studies of 8-bromo-2'-deoxyinosine and 8-bromoinosine in aqueous solutions

The reactions of hydrated electrons (e(aq) (-)) with 8-bromo-2'-deoxyinosine (8) and 8-bromoinosine (12) have been investigated by radiolytic methods coupled with product studies and have been addressed computationally by means of BB1K-HMDFT calculations. Pulse radiolysis revealed that one-electron reductive cleavage of the C--Br bond gives the C8 radical 9 or 13 followed by a fast radical translocation to the sugar moiety. Selective generation of a C5' radical occurs in the 2'-deoxyribo derivative, whereas in the ribo analogue the reaction is partitioned between the C5' and C2' positions with similar rates. Both C5' radicals undergo cyclizations, 10-->11 and 14-->15, with rate constants of 1.4 x 10(5) and of 1.3 x 10(4) s(-1), respectively. The redox properties of radicals 10 and 11 have also been investigated. A synthetically useful photoreaction has also been developed as a one-pot procedure that allows the conversion of 8 to 5',8-cyclo-2'-deoxyinosine in a high yield and a diastereoisomeric ratio (5'R)/(5'S) of 4:1. The present results are compared with data previously obtained for 8-bromoadenine and 8-bromoguanine nucleosides. Theory suggests that the behavior of 8-bromopurine derivatives with respect to solvated electrons can be attributed to differences in the energy gap between the pi*- and sigma*-radical anions.     

Synthesis of benzyl esters using 2-benzyloxy-1-methylpyridinium triflate

Triethylamine (Et3N) mediates esterification reactions between the title reagent (1) and carboxylic acids. Alcohols, phenols, amides, and other sensitive functionality are not affected; a dual role for Et3N as a promoter and a scavenger is postulated. Benzyl esters are obtained from substrates including amino acid and sugar derivatives.     

Unexpected Synthesis of 2, 2''''-[1-(4-Methoxyphenoxy)propane- 2, 2-diyl]bis(5-methoxy-3-methylbenzofuran)

Most of natural and synthetic compounds1-3 with benzofuran moieties exhibit broad spectrum bioactivities, such as antitumor, antifungal, antivirus activities; 5-lipoxygensase inhibitory activity and 5α-reductase inhibitory activity4-7. Moreover, they are also key intermediates for constructing some natural bioactive quinones8.As part of our research program focused on novel ortho-naphthofuranoquinone derivatives, various 3-substituted benzofurans were required as synthetic intermediates. Synt…     

A novel synthesis of 3-bromo-1,2,4-oxadiazoles

A novel synthesis of 3-bromo-1,2,4-oxadiazoles by 1,3-dipolar cycloaddition between bromocyanogen oxide and alkyl and aryl nitriles is described.