Upali Siriwardane

The preparation of the first α-vinylidenepenams

Abstract Benzyl esters of the first 6-vinylidenepenams have been prepared by reaction of 6-position propargylic triflates with higher order organocuprates. This methodology permits a great deal of versatility in the introduction of substituents at the terminal allenyl position.

Synthesis of Ring-Expanded Xanthines and Xanthosines Containing the Imidazo[4,5-d][1,3]diazepine Ring System

Abstract Syntheses of 4, 5, 6, 8-tetrahydro-1H, 7H-imidazo[4, 5-d] [1, 3]-diazepine-5, 8-dione (9), its 3-benzyl derivative (8), and 3- and 1-ribosyl derivatives, (12) and (13), respectively, are reported. Single-crystal x-ray analyses of 8 and 9 are also presented.

A stereocontrolled synthesis of cis-3,4-diarylisochroman-1-ones through diastereoselective reaction of benzaldehydes and α-lithio-2-cyanodiarylmethane intermediates.

Abstract A highly diastereoselective reaction of benzaldehydes and α-lithio-2-cyanodiarylmethanes is reported. Using this approach a stereocontrolled synthesis of cis-3,4-diarylisochroman-1-ones is described.

Structural and bonding investigation of the donor—acceptor complex 1-Sn(phenanthroline)-2, 3-[Si(CH3)]3]2-2,3-C2B4H4: A comparative study of the group 14 metallacarborane-Lewis base complexes

Closo-1-Sn-2,3-[Si(CH3)3]2-2,3-C2B4H4 (1) reacts with 1,10-phenanthroline to form the complex 1-(C12H8N2)Sn-2, 3-[Si(CH3)3]2-2,3-C2B4H4. When crystals of this complex were grown slowly from benzene, a crystalline modification (2) was obtained in which the unit cell consisted of four identical molecules of the base-stannacarborane and six benzene molecules of solvation. When the complex was sublimed, a second crystalline modification (3) was obtained whose unit cell consisted of two crystaliographically different molecules (3-1 and3-2). In all three forms the tin was not symmetrically bonded to the carborane but was slipped toward the boron side of the C2B3 face, and the phenanthroline molecules were oriented opposite to the cage carbons so that the plane of the base and the carborane faces gave acute dihedral angles. However, the three forms showed a great deal of variation in the extent of slippage and the magnitudes of the base-carborane dihedral angles. Since these distortions are common structural features of base-group 14-carborane and cyclopentadienyl systems, MNDO-SCF molecular orbital calculations were carried out on the model compounds 1-(C12H8N2)Sn-2,3-C2B4H6, 1-[C10H8N2)Sn-2, 3-C2B9H11, and [(C10H8N2)-SnC5(CH3)5]+ to determine what factors dictate the structures of these complexes. The results showed that competing bonding interactions give rise to a very broad minimum in energy as a function of slippage and base orientation. Small energy variations, such as those produced by crystal packing forces, could produce large structural changes. Complex2 crystallizes in the monoclinic space group P21/n witha=11.096 (9) Å,b=26.51(2) Å,c=11.729 (7) Å,β=107.43 (6) ∘,U=3291 (4) Å3, andZ=4. Full-matrix least-squares analysis converged atR=0.044 andRw=0.055. Complex3 crystallizes in the triclinic space group P¯1 witha=10.251 (3) Å,b= 13.845(9) Å;c=19.168 (9) Å,α=71.12 (5) ∘,β=89.29 (3) ∘,γ=84.62 (4) ∘,U=2562 (2) Å3, andZ=4. The structure refined atR=0.079 andRw=0.125.

Synthesis and Reaction of 7-Bromo-2-(trifluoromethyl)-10-methylphenothiazine with Nitriles and Amines under Aryne-forming Conditions

The titled compound (3) was prepared by treating commercially available 3-(trifluoromethyl)phenothiazine successively with sodium hydride, methyl iodide, and N-bromosuccinimide, and its structure was ascertained by X-ray analysis. The reaction of 3 with certain aliphatic nitriles and LDA gave typical 7- and 6-addition products via aryne (4) in ratios of ca. 85:15, 5:6, respectively. However, treatment of 3 with certain primary and secondary amines and the corresponding lithiated amide afforded a single 7-aminated product (7) in good yields in each case

Unequivocal structural assignment of the product of methylation of 4-nitro-5-styrylimidazole

The structure of one of the two regioisomeric products of methylation of 4-nitro-5-styrylimidazole has been assigned by single-crystal X-ray diffraction analyses.

The synthesis and structure of 1,2,3,4-tetrahydro-2,4,4-trimethyl-8-nitroimidazo[1,5-d] [1,2,4]triazin-1-one, C8H11N5O3: A heterocycle with a rare ring system

The title compound (IV) was isolated as a by-product during the course of purification of 4-nitroimidazol-5-(N′-methyl)hydrazide (II) by silica gel flash chromatography, employing chloroform-acetone (4:1) as the eluting solvent. The crystals are monoclinic, space groupP21/c,a=7.425(1),b=13.615(2),c=10.359(2) Å,β=97.66(1)°,dcaled=1.44 g cm−3,μ (MoKα)=1.06 mm−1,T=298 K. The number of unique reflections=2401, reflections withI≥3 σ(I)=1773;R=0.051,Rw=0.061. The bond distances inIV are: N-N, 1.419(3); N-C(=0), 1.359(3); N(H)-C(CH3), 1.457(3); N(C)-C(CH3), 1.501(3); N=C, 1.316(3); C=C, 1.368(3), N-C(=N), 1.353(3); N-C(=C), 1.367(2) Å.

Reactions of a Cyclenphosphoranide Platinum (II) Complex and the Role of Highly Nucleophilic Substituents at the Axial Positions of a Trigonal Bipyramid

Abstract (η2-cyclenP)Pt(Cl)PPh3 1 exhibits a large variety of selective reactions due to the platinum metal and cyclenphosphoranide ligand, cyclenP. Moreover, the cyclenP ligand is capable of altering many of the usual reactions and/or mechanisms at square planar platinum (II) complexes.