A concise synthetic strategy to functionalized chromenones via [5+1] heteroannulation and facile C-N/C-S/C-O bond formation with various nucleophiles

A highly efficient strategy to 2,3-substituted chromen-4H-ones has been developed. The methodology involves unexpected intramolecular heteroannulation of readily accessible substituted 2-hydroxy-ω-nitroacetophenone with carbon disulfide in the presence K₂CO₃ followed by methylation with methyl iodide. These chromenones were further reacted with various nucleophiles such as amines, thiols, and alkoxide resulting in the facile C-N, C-S, and C-O bond formation. The scope and generality have been discussed.     

The crystal structure of 5-methyl-1-(octahydro-1-iodo-1H-1-inden-4-yl)-1H-tetrazole

The title compound is C₁₁H₁₇N₄I, F.W.=330.20, monoclinic, space groupP2₁/a,a=11.586(2),b=10.617(1),c=10.417(1) Å, =94.567(2)°,Z=4,F(000)=652, (MoK)=0.7107 Å, (MoK)=2.31 mm^–1,V=1277.31 Å₃,D _C=1.71 gcm^–3,D _m=1.70 gcm^–3. The structurewassolved by Patterson and Fourier methods and refined to anR value 0.031 for 1620 observed reflections. The connectivity and conformation of the addition product ofcis-1,5-cyclononadiene and iodine azide was determined by X-ray analysis. The reaction product contains a chair-conformation cyclohexane ring that iscis fused to a cyclopentane ring. The cyclopentane ring has an envelope conformation and an equatorially oriented iodine substituent. A planar tetrazole ring is axially substituted on the cyclohexane ring. The plane of the tetrazole ring makes a dihedral angle of 69.6° with the average plane of the carbon atoms of the cyclohexane ring.     

(E)‐N‐Benzyl­idene‐3‐chloro‐4‐fluoro­aniline

The title mol­ecule, C₁₃H₉ClFN, is substantially planar. The phenyl and 3‐chloro‐4‐fluoro­phenyl rings are on opposite sides of the C=N bond. There is an intermolecular C—H?F short contact with a C?F distance of 3.348 (2) Å and a C—H?F angle of 137.4 (1)°. The mol­ecules are held in layers parallel to the bc plane.     

Stability in the presence of degeneracy and error estimation

Received February 10, 1997 / Revised version received June 6, 1998 Published online October 9, 1998     

Approximation of tricomi problem with Neumann boundary condition

Summary The Tricomi problem with Neumann boundary condition is reduced to a degenerate problem in the elliptic region with a non-local boundary condition and to a Cauchy problem in the hyperbolic region. A variational formulation is given to the elliptic problem and a finite element approximation is studied. Also some regularity results in weighted Sobolev spaces are discussed.     

Errata: On semidefinite linear complementarity problems

We correct an error in the statement of Theorem 8 in [1]. Received: January 3, 2001 / Accepted: February 26, 2001?Published online May 18, 2001     

Hopf-Lax type formula for non monotonic autonomous Hamilton Jacobi equations

We give an explicit formula for a solution of Hamilton-Jacobi equation u_t+H(u,Du)=0 in with initial condition u(x,0)=u₀(x), where p H(u,p) is convex, positively homogeneous of degree one and the Hamiltonian H need not satisfy the monotonicity condition in u.     

Kinetic and mechanistic studies of oxidation of arginine,histidine, and threonine in alkaline medium by N-chloro-N-sodio-p-toluenesulfonamide

The kinetics of oxidation of arginine, histidine, and threonine by chloramine-T (CAT) have been investigated in alkaline medium at 35°C. The rates are first order in both [CAT] and [amino acid] and inverse fractional order in [OH^?] for arginine and histidine. The rate is independent of [OH^?] for threonine. Variation of ionic strength and addition of the reaction product, p-toluenesulfonamide, or Cl^? ions had no effect on the rate. A decrease of the dielectric constant of the medium by adding methanol decreased the rate with arginine, while the rates increased with histidine and threonine. The solvent isotope effect was studied using D₂O. (k_obs)/(k_obs) was found to be 0.55 and 0.79 for arginine and histidine, respectively. The reactions were studied at different temperatures, and activation parameters have been computed. The oxidation process in alkaline medium, under conditions employed in the present investigations, has been shown to proceed via two paths, one involving the interaction of RNHCl (formed rapidly from RNCl^?), with the amino acid in a slow step to form monochloroamino acid, which subsequently interacts with another molecule of RNHCl in a fast step to give the products, p-toluenesulfonamide (RNH₂), and the corresponding nitrile of the amino acid (R'CN). The other path involves the interaction of RNCl^? with the amino acid in a similar way to give RNH₂ and R'CN. Mechanisms proposed and the derived rate laws are consistent with the observed kinetics. The rate constants predicted using the derived rate laws, as [OH^?] varies, are in excellent agreement with the observed rate constants, thus justifying these rate laws and hence the proposed mechanistic schemes.