Meganathan Nandakumar

Lewis Acid-Mediated Michaelis−Arbuzov Reaction at Room Temperature: A Facile Preparation of Arylmethyl/Heteroarylmethyl Phosphonates

A facile preparation of arylmethyl and heteroarylmethyl phosphonate esters was achieved involving a Lewis acid mediated Michaelis-Arbuzov reaction at room temperature. Interaction of arylmethyl halides/alcohols with triethyl phosphite in the presence of Lewis acid at room temperature afforded phosphonate esters in good yields.

Diels-Alder reaction of 1,3-diarylbenzo[c]furans with thiophene S,S-dioxide/indenone derivatives: a facile preparation of substituted dibenzothiophene S,S-dioxides and fluorenones.

One pot syntheses of substituted dibenzothiophene S,S-dioxides and fluorenones were successfully achieved by Diels-Alder reaction of benzo[c]furans with thiophene S,S-dioxides and indenones, respectively. Photophysical properties of representative seven- and nine-membered dibenzothiophene S,S-dioxide acenes were also reported.

Synthesis of annulated arenes and heteroarenes involving Lewis acid-mediated regioselective annulation of unsymmetrical 1,2-(diaryl/diheteroarylmethine)dipivalates.

A ZnBr(2)-mediated regioselective annulation of unsymmetrical 1,2-diarylmethinedipivalates in DCM at room temperature led to the formation of annulated arenes and heteroarenes. The annulation of the dipivalate proceeds through the intermediacy of benzylic carbocations followed by intramolecular cyclization and subsequent aromatization to give the annulated products. The annulation methodology is highly efficient for the syntheses of anthracene as well as naphtho[b]thiophene analogues.

Diethyl 1,8-diphenyl-11-oxatricyclo­[6.2.1.02,7]undeca-2,4,6-triene-9,10-dicarboxyl­ate

The title compound, C28H26O5, is the Diels–Alder adduct from 1,3-diphenylbenzo[c]furan and diethyl maleate. The molecule comprises of a fused tricyclic system containing two five-membered rings, which are in envelope conformations with the O atom at the flap, and a six-membered ring adopting a boat conformation. The dihedral angle between phenyl substituents in the 1,8-positions is 55.1 (1)°. The ethyl groups are disordered over two sets of sites, with occupancy ratios of 0.648 (9):0.352 (9) and 0.816 (1):0.184 (1). In the crystal, pairs of C—H⋯π interactions link the molecules into inversion dimers.

Synthesis and photophysical properties of benzo[c]thiophene, p-phenylene-, triphenylamine-, and pyrene-based vinylenes

ABSTRACT An efficient synthesis of benzo[c]thiophenyl/p-phenylenyl/pyrenyl phosphonate esters has been achieved using ZnBr2-catalyzed Michaelis–Arbuzov reaction of corresponding benzyl alcohol/bromides at room temperature. Horner–Wadsworth–Emmons reaction of the phosphonate esters with aryl/heteroaryl aldehydes in the presence of t-BuOK furnished the vinylenes in good yields. The absorption and emission characteristics of the synthesized vinylenes were also reported. GRAPHICAL ABSTRACT

[2-(4-Methylbenzoyl)phenyl](4-methylphenyl)methanone.

The asymmetric unit of the title compound, C22H18O2, contains one half-molecule, the complete molecule being generated by the operation of a crystallographic twofold rotation axis. The carbonyl group and the two C atoms attached to it forms interplanar angles of 23.67 (7)° with the methyl-substituted phenyl ring and 50.74 (8)° with the central ring. In the crystal, molecules are linked into infinite chains along the b-axis direction by intermolecular C—H⋯O interactions, generating R 2 2(10) graph-set motifs.

[3-Hy-droxy-methyl-1,4-bis-(4-methyl-phen-yl)naphthalen-2-yl]methanol.

In the title compound, C26H24O2, the crowded naphthalene ring system is essentially planar [maximum deviation of 0.027 (2) Å for one of the C atoms of the unsubstituted ring]. In the crystal, molecules are connected by O—H⋯O hydrogen bonds into chains along the a axis. Pairs of the oppositely oriented chains are further cross-linked by O—H⋯O hydrogen bonds, forming infinte bands of alternating R 4 4(8) dimers and R 2 2(14) motifs.

Crystal structures of three 1-oxo-1,2-dihydronaphthalene derivatives: dimethyl 4-(4-methoxyphenyl)-2-(4-methylphenyl)-1-oxo-1,2-dihydronaphthalene-2,3-dicarboxylate, dimethyl 1-oxo-2-(pyren-4-yl)-4-(thiophen-2-yl)-1,2-dihydronaphthalene-2,3-dicarboxylate and ethyl 1-oxo-2-phenyl-2,4-bis(thiophen-2-yl)-1,2-dihydronaphthalene-3-carboxylate

In the title 1-oxo-1,2-dihydronaphthalene derivatives, the cyclohexa-1,3-diene rings of the 1,2-dihydronaphthalene ring systems adopt half-chair, boat and half-chair conformations, respectively. In the crystal of the methylphenyl compound, the molecules are linked via C—H⋯O, C—H⋯π and π–π interactions, forming a double-chain structure, while in the crystals of the other two compounds, molecules are linked by π–π interactions, forming a chain structure.

Crystal structures and conformations of two Diels–Alder adduct derivatives: 1,8-bis­(thio­phen-2-yl)-14-oxa­tetra­cyclo­[6.5.1.02,7.09,13]tetra­deca-2(7),3,5-trien-10-one and 1,8-diphenyl-14-oxa­tetra­cyclo[6.5.1.02,7.09,13] tetra­deca-2,4,6-trien-10-one

The title compounds are the product of a tandem ‘pincer’ Diels–Alder reaction consisting of [2 + 2] cycloadditions between benzo[c]furan and cyclopentanone. The molecules are linked via weak C—H⋯O intermolecular hydrogen bonds, which generate (16) ring motifs in compound (I) and C(8) chains in compound (II). In both structures, the crystal packing also features C—H⋯π interactions.

Crystal structure of 2,9-diphenyl-17λ(6)-thia-tetra-cyclo-[8.7.0.0(3,8).0(11,16)]hepta-deca-1(10),2,4,6,8,11(16),12,14-octa-ene-17,17-dione.

The title compound, C28H18O2S, is composed of a naphthalene ring system fused with a benzothiophene ring and attached to two phenyl rings. The phenyl rings make dihedral angles of 70.92 (8) and 79.23 (8)° with the essentially planar naphthalene ring system (r.m.s. deviation = 0.031 Å). There is an intramolecular C—H⋯π interaction present. In the crystal, molecules are linked by C—H⋯O hydrogen bonds which generate C(7) zigzag chains running parallel to [10-1]. The chains are linked via further C—H⋯π interactions, forming a three-dimensional structure.