Michael addition of ethyl anthranilate and phenyl monothioanthranilate to acetylenic esters: experimental and theoretical results

Structural Chemistry - The reaction of ethyl anthranilate with DMAD and with methyl propiolate in dichloromethane in the presence of ethylaluminium dichloride as catalyst at room temperature gives...     

A DFT investigation of the retro-ene reactions of β-hydroxyacetylenes: concerted or stepwise mechanism

Structural Chemistry - The retro-ene reactions of β-hydroxyacetylene and its 10 derivatives have been investigated theoretically at the B3LYP/6-31+G(d) level. The reactions are found to...     

Synthesis,characterization, and insecticidal activity of new tin (IV) complexes

A three-component reaction of dimethyltin dibromide with imidazo[1,2-a]pyridine, pyridine derivatives, or isoquinoline and allyl bromide in refluxing ethanol affords the ionic complex, bis(1-allylcycloiminium) dimethyltetrabromostannate (II). The reaction involves N-allylation of cycloimine accompanied by the coordination of two bromide ions with the tin atom of dimethyltin dibromide. The complexes have been characterized by infrared and ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR studies. The X-ray crystal structure analysis of a complex reveals the tin atom to be hexacoordinated and the dimethyltetrabromostannate (II) anion having octahedral geometry. Some of the complexes tested for their insecticidal activity are found to exhibit strong activity against Tribolium castaneum insect with LC₅₀ ranging from 0.4 to 0.8 ppm.     

Diels–Alder reactions of 5,6‐dihydrothiazolo[3,2‐d][1,4,2]diazaphospholes: A DFT investigation

The density functional theory level (B3LYP/6‐311G**) computations of the Diels–Alder (DA) reactions of 5,6‐dihydrothiazolo[3,2‐d][1,4,2]‐diazaphospholes with 1,3‐butadiene and with isoprene confirm pericyclic mechanism via asynchronous transition states. The aromatic character of the transition states is established by negative nucleus independent chemical shift (NICS) values falling in the range from −14 to −16. Integration of the dienophilic >CP functionality in the 6π aromatic azaphosphole ring raises the activation energy barrier (B3LYP/6‐311++G**//B3LYP/6‐311G**) compared to that for the DA reaction of the acyclic phosphaethene, but it is lower than the activation energy barrier for the DA reaction of the corresponding 10π aromatic system, thiazolo[3,2‐d][1,4,2]diazaphospholes. The experimentally observed stereo‐ and regioselectivities in the reactions can be accounted on the basis of secondary molecular orbital (SMO) interactions detected in the respective transition structures. The attachment of an electron‐withdrawing group to the dienophilic moiety enhances both stereo‐ and regio‐ selectivities which agree well with the experimental values. Solvent (toluene) effect studied with polarizable continuum model (PCM) indicates that the stereo‐ and regioselectivities are not affected by the solvent. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:402–410, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20196