Regioselective Synthesis of Thiopyrano[3,2‐c][1]benzothiopyran‐5(2H)‐one and Thieno[3,2‐c][1]benzothiopyran‐4(2H)‐one

4‐Mercaptothiocoumarin was alkylated with different propargylic and allylic halides under phase‐transfer‐catalyzed conditions in the presence of tetrabutylammonium bromide (TBAB) or benzyl triethylammonium chloride (BTEAC) catalyst in dichloromethane–aqueous NaOH solution (1%) at room temperature. These 4‐thiopropynyl and thioallyl thiocoumarins were then refluxed in chlorobenzene and quinoline to give thiopyrano[3,2‐c][1]benzothiopyran‐5(2H)‐one and thiopyrano[3,2‐c][1]benzothiopyran‐4‐one respectively.     

Regioselective Synthesis of Polyheterocycles From 4-Cyclohex-2-ENYL-3-Hydroxy-1-Methylquinolin-2(1H)-One

4-Cyclohex-2-enyl-3-hydroxy-1-methylquinolin-2(1H)-one (4) was prepared in 90% yield by the thermal [3,3]sigmatropic rearrangement of 3-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) in refluxing chloroben-zene for 10 h. Compound (4) was cyclised through a sequence of reactions viz. i) acetylation ii) addition of bromine and iii) treatment of the acetyl dibromo compound (6) with base to give a bicyclic product (7) in 90% yield. Treatment of compound 4 with pyridine hydro-bromide perbromide in dichloromethane at 0–5° C afforded a cyclic product 8 in excellent yield. Compound 4 when treated with cold conc. sulphuric acid at 0–5° C furnished the bicyclic product 12 in 89% yield.     

Regioselective synthesis of pyrano[3,2-f]quinoline and phenanthroline derivatives using molecular iodine

A series of polysubstituted pyrano[3,2-f]quinoline and phenanthroline derivatives have been synthesized by molecular iodine-catalyzed tandem reaction of various propargylic alcohols with or without substituted amines in excellent yields. Moreover, the cyclized side products are also pyrano[3,2-f]quinoline and phenanthroline derivatives.     

Density of near-extreme events

We provide a quantitative analysis of the phenomenon of crowding of near-extreme events by computing exactly the density of states (DOS) near the maximum of a set of independent and identically distributed random variables. We show that the mean DOS converges to three different limiting forms depending on whether the tail of the distribution of the random variables decays slower than pure exponential, faster than pure exponential, or as a pure exponential function. We argue that some of these results would remain valid even for certain correlated cases and verify it for power-law correlated stationary Gaussian sequences. Satisfactory agreement is found between the near-maximum crowding in the summer temperature reconstruction data of western Siberia and the theoretical prediction.     

Level density of a bose gas and extreme value statistics

We establish a connection between the level density of a gas of noninteracting bosons and the theory of extreme value statistics. Depending on the exponent that characterizes the growth of the underlying single-particle spectrum, we show that at a given excitation energy the limiting distribution function for the number of excited particles follows the three universal distribution laws of extreme value statistics, namely, the Gumbel, Weibull, and Fréchet distributions. Implications of this result, as well as general properties of the level density at different energies, are discussed.     

Effect of grinding on the low temperature photoluminescence of certain inorganic crystals

The broadening as well as shift in the photoluminescence spectra of K₂[Pt(CN)₄] · 3 H₂O, Ba[Pt(CN)₄] · 4 H₂O, CdS:Te and Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals take place with their grinding. The original vibronic peaks at 632 and 628 nm of CdS:Te and Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals, respectively, disappear with the grinding. A new vibronic peak at 650 nm appears with grinding of Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals. It is concluded that the change in the photoluminescence spectra is attributed to the creation of dislocations during the process of grinding.     

Para Substituted Benzaldehydes as Expedient Reagents for the Oxidative Aromatization of Hydroquinoline

A Cannizzaro‐type reaction of tetrahydro‐5(1H)‐quinolinones with para substituted benzaldehydes in the presence of a base formed the corresponding quinoline and aryl methanol rather than arylidene derivatives because of the oxidation of tetrahydroquinoline and reduction of benzaldehydes as a result of unprecedented hydride transfer from tetrahydroquinoline to arylaldehydes. The reaction proceeds best with the participation of substituents with +M effect in substrate molecule.     

Practical Synthesis of N‐Alkyl‐N‐alkyloxycarbonylaminomethyl Prodrug Derivatives of Acetaminophen,Theophylline, and 6‐Mercaptopurine

We report a novel synthesis of N‐alkyl‐N‐alkyloxycarbonylaminomethyl (NANAOCAM) prodrugs of acetaminophen, theophylline, and 6‐mercaptopurine by alkylation of the corresponding drug molecule with N‐alkyl‐N‐alkyloxycarbonylaminomethyl chlorides in good yield. Most of the alkylating agents were efficiently synthesized by chloromethylation of N‐alkyl carbamic acid alkyl esters, which in turn were made from alkyl amines and alkyl chloroformates. In cases where the alkyl chloroformates were not available, synthesis of N‐alkyl carbamic acid alkyl esters was accomplished by converting an alcohol to a chloroformate or to an activated acylating agent such as acyl imidazoles or p‐nitrophenylcarbonate esters, followed by their reaction with alkyl amines.