Rajesh Shukla

Syntheses of bis- and tetra-crowned clefts and studies of their selectivities in metal ion complexation

Abstract A novel “tetra[benzo(18-crown-6)]-crowned cleft” ( 2 ) and two new “bis[benzo(15-crown-5)]-crowned clefts” ( 3 and 4 ) have been synthesized. Their respective selectivities in (i) alkali metal picrate extraction into chloroform and (ii) alkali metal perchlorate transport across bulk chloroform membranes have been determined relative to those of appropriate model compounds in each case. The observed picrate extraction selectivity order for 2 , i. e. Cs + > Rb + > K + > Na + > Li + , strongly suggests the existence of “sandwich” complexes which result from extraction cooperativity between two spatially proximate benzo(18-crown-6) units in 2 and a guest alkali metal cation. Interestingly, the corresponding selectivity order for 3 and 4 suggests that only 1 : 1 metal ion-crown ether complexes are formed. For bulk chloroform membranes, bis- and tetra-crowned clefts exhibit much more efficient transport of certain alkali metal perchlorates than do model mono-crown ether compounds.

A Simple Procedure for Preparing Annulated p-Benzoquinones. Improved Synthesis of 1,4-Dihydro-1,4-methanonaphthalene-5,8-dione

Abstract A simple and efficient two-step, one-pot synthesis of substituted 1,4-dihydro-1,4-methanonaphthalene-5,8-diones is reported. This synthesis, which utilizes readily available starting materials and inexpensive reagents, can be used to prepare 1a-1c in 70–90% overall yield. This procedure was extended successfully to prepare a more highly complex annulated p-benzoquinone i.e., 8.

Short H...H distances in norbornene derivatives

AbstractA short H· · ·H intramolecular interaction was reported previously for an anhydride of syn-sesquinorbornene. The synthesis and structure of a such an anhydride with an additional five-membered dithiole ring has been investigated. While hydrogen atom positions are not accurately located, the 1.62 Å separation indicates this molecule is a candidate for the shortest H· · ·H interaction. Two cycloadducts of norbornadiene, which literature suggests might exhibit additional short interactions, are reported also; however, the isomers with minimal intramolecular interactions are the isolated products. C22H20O3S2, 3, crystallizes in P

Acid and base promoted rearrangements of Hexacyclo[11.2.1.02,12.05,10.05.15.010,14]hexadeca-6,8-diene-4,11-dione

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Stereoselectivities of Diels-Alder cycloadditions of π-facially nonequivalent dienes to MTAD, PTAD, and N-methylmaleimide: A theoretical study

with a = 10.881(4), b = 13.712(8), C = 6.548(8) Å, α = 101.32(6), β = 107.49(5), γ = 90.49(4)°, Dcalc = 1.445 g cm−3, and Z = 2, C21H20O4Cl8, 5, in P21/n with a = 8.168(2), b = 13.488(4), c = 23.500(6) Å, β = 94.72(2)°, Dcalc = 1.597 g cm−3, and Z = 4, C21H28O4, 6, in P>

Synthesis, characterization and crystal density modeling of spiropolycyclic oxiranes

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