Rammohan Pal

A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes “on-water”

Abstract A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes by the reaction of indoles with various aromatic aldehydes “on-water” has been developed. The attractive features of this method are that in cases of aldehydes which are easily oxidized to acids, no external catalyst is necessary while in other cases a trace amount (ca. 5 mol%) of commercially available and inexpensive catalyst benzoic acid is sufficient to give good to excellent yield of products.

Two expedient ‘one-pot’ methods for synthesis of β-aryl-β-mercaptoketones over anhydrous potassium carbonate or amberlyst-15 catalyst

AbstractTwo expedient one-pot methods have been developed for synthesis of β-aryl-β-mercaptoketones using acetophenones, benzaldehydes and thiols as starting materials. The methods involve microwave irradiation (5 min) of 1:1 mixtures of acetophenones and benzaldehydes over neutral alumina supported anhydrous potassium carbonate or amberlyst-15 in the first step, and that is followed by addition of thiol to the resulting material and keeping at room temperature for 1.5 h.n Graphical AbstractAnhydrous potassium carbonate and amberlyst-15 are found to be efficient catalysts for the synthesis of β-aryl-β-mercaptoketones from acetophenones, benzaldehydes and thiols under solvent-free conditions. The experimental procedure is simple, involves shorter reaction times and results in good to excellent yield of the products.

Facile Condensation of Aromatic Aldehydes with Chroman-4-ones and 1-Thiochroman-4-ones Catalysed by Amberlyst-15 under Microwave Irradiation Condition

Different aromatic aldehydes and cinnamaldehyde undergo cross-aldol condensation with chroman-4-ones and1-thiochroman-4-ones in the presence of amberlyst-15 under microwave irradiation in solvent free condition to afford rapidly the corresponding E-3-arylidene and E-3-cinnamylidene derivatives, respectively, in high yield. This process is simple, efficient and environmentally benign.

Two efficient and green methods for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) without use of any catalyst or solvent

Two efficient and green methods for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) without use of any catalyst or solvent have been developed simply by heating (at 120°C) or microwave irradiation (300 W) of intimate mixtures of 3-methyl-l-phenyl-5-pyrazolone and aldehyde in 2:1 mole ratio.

An Efficient and Green Method for Synthesis of 2,4,5-Triarylimidazoles without Use of Any Solvent, Catalyst, or Solid Surface

An efficient and green method for synthesis of 2,4,5-triarylimidazoles without use of any catalyst or solvent has been developed simply by heating (at 130°C) of mixtures of 1,2-diketone, aromatic aldehyde, and ammonium acetate in 1u2009:u20091u2009:u20093 mole ratio.

Facile Iodine-Catalyzed Michael Addition of Indoles to α,α'-Bis(arylmethylene)cyclopentanones: An Efficient Synthesis of E-2-(3-Indolylphenylmethyl)-5-phenylmethylenecyclopentanones.

Iodine-catalyzed reaction of indoles with α,α′-bis(arylmethylene)cyclopentanones afforded one diastereomer of the corresponding Michael adducts, namely, E-2-(3-indolylphenylmethyl)-5-phenylmethylenecyclopentanones, in a good yield. The products form a new group of indole derivatives.

trans-2-Phenyl-4-thiophenoxy-3,4-dihydro-2H-1-benzothiopyran

Iodine-catalyzed cyclocondensation of cinnamaldehyde and thiophenol yields rapidly trans-2-phenyl-4-thiophenoxy-3,4-dihydro-2H-1-benzothiopyran in excellent yield with very high diastereoselectivity.

Base-promoted cyclocondensation of (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones with guanidine hydrochloride: facile synthesis of E-2-amino-4-aryl-6-(2-arylethenyl)pyrimidines

Submit Manuscript | http://medcraveonline.com classes of pyrimidines. The pharmaceutical importance of these compounds lies on the fact that they can be effectively used as analgesics, anti-inflammatory, anticonvulsant, insecticidal, herbicidal, antitubercular, anticancer and antidiabetic agents [4-6]. Also, the pyrimidine and aminopyrimidine structures are frequently-occurring motifs in commercially available drugs such as anti-atherosclerotic aronixil [7], anti-anxiolytic buspirone [8], and other medicinally relevant compounds [9,10]. Symmetrical (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones (1) and their unsymmetrical analogues (2), which could be constructed easily, also possess structural features similar to α,α’-bis(arylmethylene) cycloalkanones previously utilized by us for studying their reaction with thiourea and guanidine hydrochloride [11,12]. It is evident from the literature that the reaction of (1E,4E)-1,5diarylpenta-1,4-dien-3-ones (1 and 2) with guanidine has not been studied so far, although there are reports of cyclocondensation of varieties of α,β-unsaturated ketones with guanidine [13,14]. In this paper, we report a facile synthesis of E-2-amino-4-aryl-6-(2arylethenyl) pyrimidines by base-promoted cyclocondensation of various (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones with guanidine hydrochloride.

Schmidt Reaction of E-3-Benzylidenechromanones and E-3-Benzylidenethiochromanones

On treatment with NaN3/c. H2SO4-HOAc or NaN3/TFA, E-3-benzylidenechromanones are mostly converted to E-β-aminobenzylidenechromanones while E-3-benzylidenethiochromanones are converted to 3-benzoylthiochromones. A structurally new type of product has been isolated for the reaction of E-3-benzylidene-4′-methoxychromanone with NaN3/TFA. Mechanistic paths have been suggested for formation of the products.

NBS Oxidation of E-3-Benzylidenechromanones to 3-(α-Hydroxybenzyl)chromones and 3-Benzoylchromones

Both natural and synthetic chromones show diverse biological activities,1–7 some being in regular clinical use.8,9 Thus, the chemistry of chromones and related compounds are of interest to organic chemists with the goal of generating new biologically active molecules. We previously reported that E-3-benzylideneflavanones (4) are readily converted to 3-(α-hydroxybenzyl)flavones (5) by oxidation with NBS in CaCl2-dried CCl4 under reflux conditions.10,11 The products were probably formed through the intermediate 3-(α-bromobenzyl)flavones which underwent rapid hydrolysis with adventitious water. However, attempted isolation of such intermediate did not meet with success. In order to assess the scope of this reaction, we undertook the study of the reaction of NBS with E-3benzylidenechromanones (1) in ordinary CCl4 (commercial AR grade, which usually contains trace amount of moisture), particularly because there are very limited number of published reports of synthesis of the expected products 3-(α-hydroxybenzyl)chromones (2).12,13 Thus, when E-3-benzylidenechromanones 1a-g (1 equiv.) were refluxed in CCl4 with NBS (1 equiv.) and benzoyl peroxide (trace), 3-(α-hydroxybenzyl)chromones (2) were formed in very good yields along with 3-benzoylchromones (3) as minor products (Scheme 1, Table 1). Since the formation of 3 indicated that a further oxidation had occurred, this led us to study the reaction of 1 with double the amount of NBS which led to 3 as the major product and 2 the minor one (Table 1). When the 3-(α-hydroxybenzyl)chromones (2) were treated separately with NBS (1 equiv.), they were completely converted to 3benzoylchromones (3) (Table 2). All the new compounds of the series 2 and 3 gave satisfactory combustion analyses and spectral data. This study was extended to E-3-benzylideneflavanones (4) with two molar equivalents of NBS; Scheme 2, Table 3 shows that, except for 4d, all the substrates gave 3benzoylflavones (6), albeit in low yields. Oxidation of 5a-c [NBS (1 equiv.), (PhCOO)2