No abstract

Nitration of aromatic Compounds is triggered by Vilsmeier-Haack reagent (DMF/POCl3) or (DMF/SOCl2) in the presence of KNO3 or NaNO2 under conventional and non-conventional conditions. The reactions af- forded corresponding Nitro derivatives in very good yield with high regioselectivity. The results obtained in non-conventional methods (Micro wave irradiation, Grinding, Sonication) are comparable with those ob- tained under conventional conditions, but the reaction times of former conditions are substantially shorter than that of the latter

Acetylation and benzoylation reactions of certain aromatic aldehydes, ketones with Vilsmeier-Haack Reagents using Acetamide and Oxychloride (SOCl 2 or POCl 3 ) under conventional (thermal) and non conventional [microwave irradiated (MIR), ultrasonic assisted and solvent free mortar pestle (grinding)] conditions. Reactions afforded good to excellent yields of products with both the VH reagents, reaction times were fairly less in the case of [amide/POCl 3 ] than those of [amide/SOCl 2 ] reagent. Reactions are dramatically accelerated in under sonicated and microwave irradiations with a trend: MIR (few seconds) >> Sonication (minutes) > Grinding (min) >> thermal (several hrs).

VilsmeierÀHaack (VH) acetylation reactions with benzaldehydes or acetophenones in MeCN followed second-order kinetics and afforded acetyl derivatives under kinetic conditions, irrespective of the nature of the oxychloride (SOCl 2 or POCl 3 ) used for the preparation of the VH reagent along with acetamide. The present finding contributes to the understanding of the nature of the reactive species of the VH reagent as well as of the acetylation mechanism.Introduction. -The VilsmeierÀHaack reagent (VHR) is a versatile reactant in organic synthesis [1 -6]. In earlier investigations, it is reported that formylation can be achieved more conveniently by the VilsmeierÀHaack (VH) reaction than by the ReimerÀTiemann, GattermannÀKoch, or Duffs formylation methods [7 -12]. In the recent past, several formylation, acetylation, and bromination reactions under VH conditions have been reported from our group and others [13 -20]. For example, benzanilide (¼ N-phenylbenzamide) and N,N-dimethylaniline (¼ N,N-dimethylbenzenamine) react with phosphorus oxychloride (¼ phosphoric trichloride; POCl 3 ) to produce an unsymmetrical diaryl ketone [17]. Similarly, anthracene can be formylated exclusively at the 9-position [19]. Under VH conditions, formylation of 1H-indole [18] takes place at room temperature exclusively at C(3), to afford 1H-indole-3-carboxaldehyde. Since the pyrrole part is the most reactive portion of 1H-indole, nucleophilic substitution of the fused carbocyclic (benzene) ring can take place only after N(1), C(2), and C(3) are substituted. This was supported by the fact that at C(3) position of 1H-indole, electrophilic substitution is 10 13 times faster than that of benzene.Earlier publications from our group elaborated kinetic and mechanistic aspects of the formylation of coumarin derivatives (i.e., 4H-1-benzopyran-4-one derivatives) [3] [17] and formation of a chromen-4-one (¼ 4H-1-benzopyran-4-one) and its subsequent formylation products from 2-hydroxyacetophenone (¼ 1-(2-hydroxyphenyl)ethanone; 2-OHap) [3] [17] under VH conditions in various solvent media. These studies revealed second-order kinetics with first-order in [substrate] and first-order in [VHR] reagent. The reaction rates altered nonlinearly with an increase in the dielectric constant of the medium, and the data did not fit completely well with either Amis or Kirkwoods theories of ionÀdipole-and dipoleÀdipole-type reactions. On the basis of kinetic and spectroscopic results, participation of the VH adduct and substrate

Bromination of 2‐alkoxynaphthalene (2‐ANP) and its derivatives with trimethyl benzyl ammonium tribromide (TMBATB) did not proceed smoothly even under reflux conditions. But the addition of microconcentrations of cetyltrimethyl ammonium bromide (CTAB) to the reaction afforded dramatic rate accelerations as well as good‐to‐excellent yield of the products ranging from 70% to 90%. Reactions underwent regioselective monobromination at 1‐position of 2‐alkoxynaphthalene. The rate of bromination has been followed conductometrically. The reaction kinetics indicated first‐order kinetics in [2‐ANP] as well as in [TMBATB]. Kinetic results in the presence of CTAB were explained on the basis of the Raghavan–Srinivasan model as applied to micelle‐mediated bimolecular reactions.