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Papers by Venkat Chintareddy
The Journal of Organic Chemistry, 2008
All reactions were performed under an atmosphere of argon in oven-dried glassware. Toluene and te... more All reactions were performed under an atmosphere of argon in oven-dried glassware. Toluene and tetrahydrofuran (THF) were freshly distilled over sodium/benzophenone and stored over 4 Å molecular sieves under an argon atmosphere. 1 H (300 or 400 Hz) and 13 C (100.6 MHz) NMR spectra were recorded in CDCl 3 (unless otherwise stated); the chemical shifts are referenced to the residual peaks of CHCl 3 in CDCl 3. 31 P NMR spectra were recorded at ambient temperature on 400 MHz spectrometer using standard procedures. Thin layer chromatography (TLC) was performed using commercially prepared 60 mesh silica gel plates visualized with shortwavelength UV light (254 nm). Column chromatography was performed on silica gel (40 140 mesh) for the purification of aryl amines. Celite was used for the purification of enamines and imines. Electron impact ionization experiments were performed on a triple quadrupole mass spectrometer fitted with a EI/CI ion source. Accurate mass measurements were performed using a double focusing mass spectrometer. The reported yields are isolated yields and are the average of two runs. All commercially available reagents were used as received. Ligands 3a b were prepared as stated in the manuscript, whereas the synthesis of 3c and 3d are reported herein. All products described in Tables 1 8 and Scheme 1 are known in the literature (unless indicated otherwise) and were characterized by comparing their 1 H and 13 C NMR to the previously reported data. In all cases, the comparisons were very favorable. New compounds (Table 2, entry 4; Table 2, entry 12, Table 5, entries 11-13, Table 7, entries 1, 12, 13 and 14) and compounds 3c and 3d were characterized by 1 H, 13 C, mass (EI) and HRMS analysis. Proton NMR spectra compared favorably for the compound shown in Table 6, entry 4 with the proton spectrum in the literature. Since 13 C NMR and HRMS data were not available in the literature, these are now given in the Supporting Information. Literature references for yield comparisons with our
![Research paper thumbnail of ChemInform Abstract: P[N(i-Bu)CH2CH2]3N: Nonionic Lewis Base for Promoting the Room-Temperature Synthesis of α,β-Unsaturated Esters, Fluorides, Ketones, and Nitriles Using Wadsworth-Emmons Phosphonates](https://attachments.academia-assets.com/43905803/thumbnails/1.jpg)
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![Research paper thumbnail of ChemInform Abstract: P[N(i-Bu)CH2CH2]3N: Nonionic Lewis Base for Promoting the Room-Temperature Synthesis of α,β-Unsaturated Esters, Fluorides, Ketones, and Nitriles Using Wadsworth—Emmons Phosphonates](https://attachments.academia-assets.com/43905804/thumbnails/1.jpg)
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The Journal of Organic Chemistry, 2010
The bicyclic triaminophosphine P(RNCH(2)CH(2))(3)N (R = i-Bu, 1c) serves as an effective promoter... more The bicyclic triaminophosphine P(RNCH(2)CH(2))(3)N (R = i-Bu, 1c) serves as an effective promoter for the room-temperature stereoselective synthesis of α,β-unsaturated esters, fluorides, and nitriles from a wide array of aromatic, aliphatic, heterocyclic, and cyclic aldehydes and ketones, using a range of Wadsworth-Emmons (WE) phosphonates. Among the analogues of 1c [R = Me (1a), i-Pr (1b), Bn (1d)], 1a and 1b performed well, although longer reaction times were involved, and 1d led to poorer yields than 1c. Functionalities such as cyano, chloro, bromo, methoxy, amino, ester, and nitro were well tolerated. We were able to isolate and characterize (by X-ray means; see above) the reactive WE intermediate species formed from 2b and 1c.
Journal of Molecular Catalysis A: Chemical, 2007
... Diphenyl sulfone [26] (Table 5, entry 5) 2.4.6. Dibenzothiophene-5,5-dioxide [26] (Table 5 ..... more ... Diphenyl sulfone [26] (Table 5, entry 5) 2.4.6. Dibenzothiophene-5,5-dioxide [26] (Table 5 ... unreacted H 2 O 2 . The reaction mixture was filtered to remove solid MnO ... Analytically pure compound was obtained after column chromatography (silica gel, using hexane/ethyl acetate ...
RSC Nanoscience & Nanotechnology, 2012
Journal of Molecular Catalysis A: Chemical, 2012
ABSTRACT An efficient method for the oxidation of benzylic and secondary aromatic alcohols into t... more ABSTRACT An efficient method for the oxidation of benzylic and secondary aromatic alcohols into their corresponding aldehydes or ketones has been achieved by using ruthenium supported magnesium–lanthanum mixed oxide as a heterogeneous catalyst in toluene, with molecular oxygen as the sole oxidant. This catalyst can also be operated in solvent free conditions at 393 K and reused for five cycles with consistent yield and selectivity.
Catalysis Letters, 2000
The facile catalytic oxidation of sulfides to sulfoxides has been achieved with VO(acac) 2 suppor... more The facile catalytic oxidation of sulfides to sulfoxides has been achieved with VO(acac) 2 supported on titania using tert-butyl hydroperoxide (TBHP) as an oxidant in dichloromethane in quantitative yields at room temperature. The catalyst is reusable and tested for five cycles without significant loss of activity and selectivity.
Bioresource Technology, 2012
This study highlights the potential of oleaginous fungus, Mucor circinelloides in adsorbing/assim... more This study highlights the potential of oleaginous fungus, Mucor circinelloides in adsorbing/assimilating oil and nutrients in thin stillage (TS), and producing lipid and protein-rich fungal biomass. Fungal cultivation on TS for 2 days in a 6-L airlift bioreactor, resulted in a 92% increase in oil yield from TS, and 20 g/L of fungal biomass (dry) with a lipid content of 46% (g of oil per 100g dry biomass). Reduction in suspended solids and soluble chemical oxygen demand (SCOD) in TS were 95% and 89%, respectively. The polyunsaturated fatty acids in fungal oil were 52% of total lipids. Fungal cells grown on Yeast Malt (YM) broth had a higher concentration of γ-linolenic acid (17 wt.%) than those grown on TS (1.4 wt.%). Supplementing TS with crude glycerol (10%, v/v) during the stationary growth phase led to a further 32% increase (from 46% to 61%) in cellular oil content.
Advanced Synthesis & Catalysis, 2005
A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stab... more A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stabilization of PdCl 4 2− with nanocrystalline MgO followed by reduction. This ligand-free heterogeneous nanocrystalline MgO-stabilized nanopalladium [NAP Mg Pd(0)] catalyst using the basic ...
Advanced Synthesis & Catalysis, 2008
An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters... more An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters via sequential Heck coupling and hydrogenation of the alkenyl double bond in one pot with a single recyclable catalyst under mild conditions has been realised. The catalyst was recovered by simple filteration and reused for several cycles with consistent activity.
The Journal of Organic Chemistry, 2008
By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an el... more By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an electronically diverse array of aryl bromides and chlorides possessing base-sensitive substituents (nitro, ester, and keto) provide coupling products with bulky aryl amines in good to excellent yields. Aryl halides possessing other functional groups including cyano, amino, trifluoromethyl, and phenol, coupled with equal ease, producing highly functionalized amines in good to excellent yields. Moreover, an aryl chloro group can be preserved in the presence of a bromo substituent under our reaction conditions. BOC-protected amines also participated efficiently. Heterocyclic bromides and chlorides underwent clean couplings with amines in excellent yields. An important strength of our protocol is the use of lower palladium loadings than those reported earlier, without compromising yields. The air-stable palladium complex (eta3-cinnamyl)PdCl.(3a) (5) was also employed successfully in C-N coupling reactions while the crotyl analogue was less efficacious. The 3a/Pd(OAc)2 catalyst system promotes, for the first time, efficient coupling of vinyl bromides with a variety of amines to produce imines and enamines at room temperature.
The Journal of Organic Chemistry, 2008
All reactions were performed under an atmosphere of argon in oven-dried glassware. Toluene and te... more All reactions were performed under an atmosphere of argon in oven-dried glassware. Toluene and tetrahydrofuran (THF) were freshly distilled over sodium/benzophenone and stored over 4 Å molecular sieves under an argon atmosphere. 1 H (300 or 400 Hz) and 13 C (100.6 MHz) NMR spectra were recorded in CDCl 3 (unless otherwise stated); the chemical shifts are referenced to the residual peaks of CHCl 3 in CDCl 3. 31 P NMR spectra were recorded at ambient temperature on 400 MHz spectrometer using standard procedures. Thin layer chromatography (TLC) was performed using commercially prepared 60 mesh silica gel plates visualized with shortwavelength UV light (254 nm). Column chromatography was performed on silica gel (40 140 mesh) for the purification of aryl amines. Celite was used for the purification of enamines and imines. Electron impact ionization experiments were performed on a triple quadrupole mass spectrometer fitted with a EI/CI ion source. Accurate mass measurements were performed using a double focusing mass spectrometer. The reported yields are isolated yields and are the average of two runs. All commercially available reagents were used as received. Ligands 3a b were prepared as stated in the manuscript, whereas the synthesis of 3c and 3d are reported herein. All products described in Tables 1 8 and Scheme 1 are known in the literature (unless indicated otherwise) and were characterized by comparing their 1 H and 13 C NMR to the previously reported data. In all cases, the comparisons were very favorable. New compounds (Table 2, entry 4; Table 2, entry 12, Table 5, entries 11-13, Table 7, entries 1, 12, 13 and 14) and compounds 3c and 3d were characterized by 1 H, 13 C, mass (EI) and HRMS analysis. Proton NMR spectra compared favorably for the compound shown in Table 6, entry 4 with the proton spectrum in the literature. Since 13 C NMR and HRMS data were not available in the literature, these are now given in the Supporting Information. Literature references for yield comparisons with our
The Journal of Organic Chemistry, 2010
The bicyclic triaminophosphine P(RNCH(2)CH(2))(3)N (R = i-Bu, 1c) serves as an effective promoter... more The bicyclic triaminophosphine P(RNCH(2)CH(2))(3)N (R = i-Bu, 1c) serves as an effective promoter for the room-temperature stereoselective synthesis of α,β-unsaturated esters, fluorides, and nitriles from a wide array of aromatic, aliphatic, heterocyclic, and cyclic aldehydes and ketones, using a range of Wadsworth-Emmons (WE) phosphonates. Among the analogues of 1c [R = Me (1a), i-Pr (1b), Bn (1d)], 1a and 1b performed well, although longer reaction times were involved, and 1d led to poorer yields than 1c. Functionalities such as cyano, chloro, bromo, methoxy, amino, ester, and nitro were well tolerated. We were able to isolate and characterize (by X-ray means; see above) the reactive WE intermediate species formed from 2b and 1c.
Journal of Molecular Catalysis A: Chemical, 2007
... Diphenyl sulfone [26] (Table 5, entry 5) 2.4.6. Dibenzothiophene-5,5-dioxide [26] (Table 5 ..... more ... Diphenyl sulfone [26] (Table 5, entry 5) 2.4.6. Dibenzothiophene-5,5-dioxide [26] (Table 5 ... unreacted H 2 O 2 . The reaction mixture was filtered to remove solid MnO ... Analytically pure compound was obtained after column chromatography (silica gel, using hexane/ethyl acetate ...
RSC Nanoscience & Nanotechnology, 2012
Journal of Molecular Catalysis A: Chemical, 2012
ABSTRACT An efficient method for the oxidation of benzylic and secondary aromatic alcohols into t... more ABSTRACT An efficient method for the oxidation of benzylic and secondary aromatic alcohols into their corresponding aldehydes or ketones has been achieved by using ruthenium supported magnesium–lanthanum mixed oxide as a heterogeneous catalyst in toluene, with molecular oxygen as the sole oxidant. This catalyst can also be operated in solvent free conditions at 393 K and reused for five cycles with consistent yield and selectivity.
Catalysis Letters, 2000
The facile catalytic oxidation of sulfides to sulfoxides has been achieved with VO(acac) 2 suppor... more The facile catalytic oxidation of sulfides to sulfoxides has been achieved with VO(acac) 2 supported on titania using tert-butyl hydroperoxide (TBHP) as an oxidant in dichloromethane in quantitative yields at room temperature. The catalyst is reusable and tested for five cycles without significant loss of activity and selectivity.
Bioresource Technology, 2012
This study highlights the potential of oleaginous fungus, Mucor circinelloides in adsorbing/assim... more This study highlights the potential of oleaginous fungus, Mucor circinelloides in adsorbing/assimilating oil and nutrients in thin stillage (TS), and producing lipid and protein-rich fungal biomass. Fungal cultivation on TS for 2 days in a 6-L airlift bioreactor, resulted in a 92% increase in oil yield from TS, and 20 g/L of fungal biomass (dry) with a lipid content of 46% (g of oil per 100g dry biomass). Reduction in suspended solids and soluble chemical oxygen demand (SCOD) in TS were 95% and 89%, respectively. The polyunsaturated fatty acids in fungal oil were 52% of total lipids. Fungal cells grown on Yeast Malt (YM) broth had a higher concentration of γ-linolenic acid (17 wt.%) than those grown on TS (1.4 wt.%). Supplementing TS with crude glycerol (10%, v/v) during the stationary growth phase led to a further 32% increase (from 46% to 61%) in cellular oil content.
Advanced Synthesis & Catalysis, 2005
A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stab... more A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stabilization of PdCl 4 2− with nanocrystalline MgO followed by reduction. This ligand-free heterogeneous nanocrystalline MgO-stabilized nanopalladium [NAP Mg Pd(0)] catalyst using the basic ...
Advanced Synthesis & Catalysis, 2008
An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters... more An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters via sequential Heck coupling and hydrogenation of the alkenyl double bond in one pot with a single recyclable catalyst under mild conditions has been realised. The catalyst was recovered by simple filteration and reused for several cycles with consistent activity.
The Journal of Organic Chemistry, 2008
By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an el... more By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an electronically diverse array of aryl bromides and chlorides possessing base-sensitive substituents (nitro, ester, and keto) provide coupling products with bulky aryl amines in good to excellent yields. Aryl halides possessing other functional groups including cyano, amino, trifluoromethyl, and phenol, coupled with equal ease, producing highly functionalized amines in good to excellent yields. Moreover, an aryl chloro group can be preserved in the presence of a bromo substituent under our reaction conditions. BOC-protected amines also participated efficiently. Heterocyclic bromides and chlorides underwent clean couplings with amines in excellent yields. An important strength of our protocol is the use of lower palladium loadings than those reported earlier, without compromising yields. The air-stable palladium complex (eta3-cinnamyl)PdCl.(3a) (5) was also employed successfully in C-N coupling reactions while the crotyl analogue was less efficacious. The 3a/Pd(OAc)2 catalyst system promotes, for the first time, efficient coupling of vinyl bromides with a variety of amines to produce imines and enamines at room temperature.