Tarun Ghosh

Study of differences in the reactivity of alkyl and aryl nitrones derived from 4-oxo-4H-1-benzopyran-3-carboxaldehyde

On hydrolysis with 70% H2SO4, aliphatic nitrones 2a–d produce the corresponding carboxylic acids 4 but aromatic nitrones 2e, f give aldehyde 1. On heating under reflux in dry MeOH, 2a–d rearrange to 3a–d but aromatic nitrones 2e, f remain unchanged.

Reaction of sarcosine with chromone-3-carbaldehyde and 6,6‘-(polymethylenedioxy)di(chromone-3-carbaldehyde)

On treatment with N-methylglycine in DMF, the chromone-3-carbaldehydes 1a–c produce 3-[3-(2-hydroxybenzoyl)-1-methyl-2,5-dihydropyrrol-2-yl]-4H-chromen-4-ones 10a–c and the deformylated products 9a–c, whereas the bis-chromone derivatives 12a–c give the bis[3-(2-hydroxybenzoyl)-1-methylpyrrole] structures 13a–c.

A facile transformation of 2-aminochromone to 4-chlorocoumarin and its reaction with ethylenediamine

2-Aminochromones 1a–c and 8a–c are converted into 4-chlorocoumarins 2a–c and 9a–c. On treatment with ethylenediamine, 2a–c produce 2,3,4,5-tetrahydro-7-(2′-hydroxyphenyl)-1,4-diazepin-5-one 3a,b and 4-(2-aminoethyl) aminocoumarin 4b,c in ethanol; while in DMF 9a–c give the bis[4-(2-formamidoethyl)aminocoumarins 10a–c.

Chemoselective Reduction of Some Condensates derived from Chromone-3-carbaldehyde using Sm and Zn

Abstract Condensates 4–6 undergo reductive dimerization with Sm in THF containing aqueous NH4Cl to produce 7–9, whereas with Zn under similar reaction condition 3–5 produce 10–12.

Synthesis and reactivity of 3-(1-hydroxy-3-buten-1-yl)chromone

Zn-induced allylation of chromone-3-carbaldehyde 1 produces 3-(1-hydroxy-3-butene-1-yl)chromone 2, which gives back 1 on treatment with formalin under acidic conditions, and reacts differently towards nitrogenous nucleophiles.

Al/Hg - mediated reductive dimerisation of 3-methoxycarbonyl-4-oxo-4H-1-benzopyran

Aluminium amalgam – mediated reductive dimerisation of 3-methoxycarbonyl-4-oxo-4H-1-benzopyran produced two sets of diastereomeric bichromones coupled through 2,2′ and 2,4′- positions; the latter set of diastereomers underwent diastereoconvergent dehydration to produce Z-3,3′-dimethoxycabonyl-3H-2,4′-bi[1-benzopyran-2-ylidene]-4-one.