Kannupal Srinivasan

Rearrangements of bicyclic-δ-hydroxy-α,β-enones—IV : Base catalysed rearrangements of some bicyclic-α-substituted-δ-hydroxy-α,β-enones

The hydroxy enones 5a, 5b, 5c, 4d, 4a and 4b rearrange when treated with aqueous alkali to the diones 6a, 6b, 8 and 13 and acids 9 and 12 respectively. The diones 2 and 6a are also formed by thermal rearrangement of enones 1a and 5a.

Rearrangements of bicyclic δ-hydroxy-α,β-enones—III : Syntheses of substituted 1,2-benzocyclooct-1-en-6-ones

The earlier structural assignment as 2 for the dione obtained by the base treatment of 1a or 1b is confirmed. Syntheses of substituted 1,2-benzocyclooct-1-en-6-ones are reported.

Self-complementary Tetracationic Cyclophanes Containing 4,4′-Bipyridinium and 2,5-Dimethoxy-1,4-xylyl Subunits

4,4′-Bipyridinium-based tetracationic cyclophanes containing a 2,5-dimethoxy-1,4-xylyl unit were synthesized by using either m-terphenyl building blocks or incorporating a 4-hydroxy benzyl spacer between the complementary subunits. The cyclophanes show weak intramolecular charge-transfer (CT) bands in the visible region and one of the cyclophanes formed a green-coloured CT complex with ferrocene with an association constant (K a) of 6.3 M−1. The electrochemical parameters obtained for the cyclophanes indicate that all the redox processes are reversible.

Synthesis of Azobenzenophanes with a Large Molecular Cavity

The design and synthesis of four large-cavity azobenzenophanes, capable of forming photochemically controllable complexes with organic guest molecules, are described. These azobenzenophanes, possessing m-terphenyl, aromatic carbonyl, and chiral BINOL spacers, were synthesized from the corresponding bisphenols and dibromides using simple O-alkylation methodology. A preliminary photochemical study was carried out on the aromatic carbonyl spacer containing azobenzenophane, and the isosbestic points for the cis–trans isomerization process appeared at 319 and 419 nm.

Synthesis of axially chiral dendrimers containing meta-terphenyl peripheral groups and a chiral binol core

Fréchet-type poly(arylether) dendritic bromides carrying m-terphenyl peripheral groups were synthesised up to second generation by convergent methodology. Simple O-alkylation of chiral (S)-BINOL with the dendritic bromides afforded the corresponding axially chiral dendrimers. The molar optical rotation values of the dendrimers become increasingly negative as the dendrimer generation increases.

Self-complementary azolophanes

By incorporating a m-terphenyl spacer, azolophanes containing imidazole, benzimidazole or benzotriazole and 2, 5-dimethoxy-1,4-xylyl subunits were synthesised by N-alkylation followed by quarternisation. The electrochemical parameters obtained for the azolophanes indicated that the redox processes are quasireversible.

Synthesis and Electrochemical Properties of [2]Rotaxanes with meta-Terphenyl and meta-Terphenyl-Capped Dendritic Stoppers

A meta-terphenyl moiety has been employed as a stopper in a Stoddart-type [2]rotaxane, which is formed in a remarkably high yield due to the additional templating effect of the stoppers. Making use of the recognition between bis(pyridinium)ethane and dibenzo-24-crown-8 ether, the [2]rotaxanes with m-terphenyl and m-terphenyl-capped dendritic stoppers have been synthesized by a threading procedure. The [2]rotaxane 7 displays two bielectronic redox waves while the [2]rotaxanes 10 and 11 show four distinct monoelectronic redox waves.