Anil Saikia - Academia.edu (original) (raw)
Papers by Anil Saikia
The Journal of Organic Chemistry, 2017
Bismuth trifluoromethanesulfonate (Bi(OTf)3) can be efficiently used for the preparation of dihyd... more Bismuth trifluoromethanesulfonate (Bi(OTf)3) can be efficiently used for the preparation of dihydropyrans from β-allenols and aldehydes by oxonium-ene reaction in good yields. The reaction is highly regioselective. On the other hand, the same reaction with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at-45 o C affords hexahydropyrano[4,3b]pyran skeleton in moderate yields.
Synlett, Jul 8, 2022
A variety of oxygen, nitrogen and sulfur heterocyclic compounds are synthesized via one-pot multi... more A variety of oxygen, nitrogen and sulfur heterocyclic compounds are synthesized via one-pot multicomponent Prins, aza-Prins, thia-Prins, oxonium-ene, iminium-ene and thionium-ene cyclization reactions. The reactions proceeds with high diastereo- and regioselectivity. Importantly, C–C, C–N, C–O and C–S bonds are formed in a singsle step. These procedures are extended for the synthesis of biologically active molecules and natural products.1 Introduction2 Prins Cyclization Reactions3 Oxonium-Ene Cyclization Reactions4 Conclusion
The Journal of Organic Chemistry, 2001
It was observed that the reaction of CFCl3 with thiophenoxide gave only 10% of the corresponding ... more It was observed that the reaction of CFCl3 with thiophenoxide gave only 10% of the corresponding thioether. On the other hand, these thioethers could be prepared in excellent yield from diaryl disulfides and CFCl3 in the presence of sodium hydroxymethanesulfinate in aqueous DMF at 4 atm pressure of nitrogen. Dechlorination of the thioether (PhSCFCl2) with different reducing agents were studied. Most of the reducing agents eliminated both fluorine and chlorine functionalities or gave the hydrolyzed products. But its sulfone on treatment with Zinc in methanol gave monochlorofluoromethyl and fluoromethyl phenyl sulfone in good yields. Darzens reaction of these compounds was also studied.
Chemical Communications
A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazoli... more A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent...
Journal of Organic Chemistry, Aug 31, 2021
An efficient methodology has been developed for the synthesis of tetra- and pentasubstituted pyrr... more An efficient methodology has been developed for the synthesis of tetra- and pentasubstituted pyrroles via oxidative self-dimerization of N-propargylamines catalyzed by silver benzoate in the presence of K2S2O8 in good yields. The protocol provides a simple route for the synthesis of both tetra- and pentasubstituted pyrroles with two carbonyl groups in the side chain. The methodology can be extended toward the synthesis of pyrrolo[3,4-d]pyridazine.
![Research paper thumbnail of ChemInform Abstract: A Novel Synthesis of Oxabicyclo[3.3.1]nonanone via (3,5)-Oxonium-Ene Reaction](https://attachments.academia-assets.com/112844400/thumbnails/1.jpg)
](ChemInform, Aug 12, 2010
A Novel Synthesis of Oxabicyclo[3.3.1]nonanone via (3,5)-Oxonium-Ene Reaction.-Higher yields are ... more A Novel Synthesis of Oxabicyclo[3.3.1]nonanone via (3,5)-Oxonium-Ene Reaction.-Higher yields are obtained when aliphatic aldehydes are used compared with the aromatic ones [cf. (III)]. The same type of products are constructed by using the epoxide substrates instead of aldehydes [cf.
Journal of Organic Chemistry, Jul 21, 2023
Journal of Organic Chemistry, Feb 22, 2023
ACS omega, Jan 18, 2018
Indium(III) chloride can be efficiently used for the synthesis of 4-vinylpyrrolidine from N-tethe... more Indium(III) chloride can be efficiently used for the synthesis of 4-vinylpyrrolidine from N-tethered alkynealkenol in good yields. The reaction is highly stereo-and regioselective.
Organic and Biomolecular Chemistry, 2021
A simple methodology for the regioselective synthesis of substituted dibenzocyclohepta[1,2-a]naph... more A simple methodology for the regioselective synthesis of substituted dibenzocyclohepta[1,2-a]naphthalenes from phenylacetaldehydes and ortho-alkynyl benzyl alcohols in the presence of a Lewis acid has been developed.
![Research paper thumbnail of Intramolecular Pictet-Spengler Reaction of Cyclic Iminium ions: A Novel Access to Benzo[1,4]oxazepine-Fused Tetrahydroisoquinoline and Tetrahydro-β-carboline Analogues](https://attachments.academia-assets.com/112844396/thumbnails/1.jpg)
](Asian Journal of Organic Chemistry, Jul 7, 2017
A simple and efficient approach has been developed for the synthesis of benzo[1,4]oxazepino-fused... more A simple and efficient approach has been developed for the synthesis of benzo[1,4]oxazepino-fused tetrahydroisoquinoline and tetrahydro-β-carboline derivatives via one-pot cascade reaction sequence. This reaction involves the intramolecular Pictet-Spengler reaction of cyclic iminium ions, which were generated in situ via trifluoroacetic acid (TFA) mediated deprotection of acetal derived from β-arylethylamines and 2-(2,2-diethoxyethoxy)benzaldehyde. All reactions produced a novel library of complex fused polyheterocyclic compounds in good to excellent yields.
Journal of Organic Chemistry, Sep 10, 2014
Indium triflate can be efficiently used for Prins cyclization of acrylyl enol ethers to give tetr... more Indium triflate can be efficiently used for Prins cyclization of acrylyl enol ethers to give tetrahydrofuran ring stereoand regioselectively in good yields. The formation of five-membered rings is against the Baldwin's rule.
ChemInform, Jun 24, 2010
Titanium Tetrafluoride: An Efficient Lewis Acid and Fluorinating Agent for Stereoselective Synthe... more Titanium Tetrafluoride: An Efficient Lewis Acid and Fluorinating Agent for Stereoselective Synthesis of 4-Fluorotetrahydropyran.-Titanium tetrafluoride efficiently promotes the stereoselective formation of 4-fluoropyrans via Prins cyclization. The method is general and can be used both for aldehydes and ketones. The conformations of the di-and tri-substituted tetrahydropyrans are proved by NOE experiments and X-ray analysis. A brief discussion of the mechanism is given as well.
![Research paper thumbnail of ChemInform Abstract: Short Enantioselective Syntheses of Both 2,7-Dimethyl-1,6-dioxaspiro[4.6]undecane and 2,7-Diethyl-1,6-dioxaspiro[4.6]undecane Using Functionalized Nitroalkane Synthons](https://attachments.academia-assets.com/112844393/thumbnails/1.jpg)
](ChemInform, Jun 7, 2010
w-Nitro ketoaliphatic compounds 3a and 3b, prepared by a new and efficient route, have been elabo... more w-Nitro ketoaliphatic compounds 3a and 3b, prepared by a new and efficient route, have been elaborated to short syntheses of both 2,7-dimethyl-1,6-dioxaspiro[4.6]undecane, [(2S,5R,7S)-1a] and 2,7-diethyl-1,6-dioxaspiro[4.6]undecane [(2S,5R,7S)-1b], the pheromones produced by Andrena haemorrhoa and Andrena wilkella, respectively.
Synlett, 2012
The reaction of aldehyde with allylsilane in acetonitrile mediated by boron trifluoride etherate ... more The reaction of aldehyde with allylsilane in acetonitrile mediated by boron trifluoride etherate generated 4-aminotetrahydropyrans in good yields. The product is highly stereoselective. Multicomponent reactions are gaining interest in organic synthesis due to its ability to form multiple bonds in a single step. 1 Substituted tetrahydropyrans are important targets because of their presence in many natural products. 2 These tetrahydropyrans are prepared by hetero-Diels-Alder methods, 3 manipulation of carbohydrates, 4 Prins cyclization, 5 and intramolecular Michael reactions. 6 Although there are a few methods for the synthesis of 4-halo-, 7 4-thio-, 8 4-azido-, 9 4-aryl-, 10 and 4-hydroxytetrahydropyran, 5e,f,7d,11 methods for the synthesis of 4-aminotetrahydropyran are limited. 12 In this paper, an efficient method for the synthesis of 4 aminotetrahydropyran from aldehyde, trimethylallylsilane, and acetonitrile mediated by BF 3 ‚ Et 2 O is disclosed (Scheme 1). Thus, when benzaldehyde was subjected to react with allyltrimethylsilane in acetonitrile in the presence of boron trifluoride etherate, 4-acetamido-2,6-diphenyltetrahydrofuran was obtained in 70% yield.
ChemistrySelect, Jun 1, 2016
Propargyl amine can be efficiently converted to pyrazole N‐oxide from the reaction of sodium nitr... more Propargyl amine can be efficiently converted to pyrazole N‐oxide from the reaction of sodium nitrite in acetic acid catalysed by AgOTf in excellent yields. The pyrazole N‐oxides can be converted into pyrazole by treatment of phosphorous trichloride in refluxing chloroform. The pyrazole N‐oxide could be converted to highly substituted 4‐chloropyrazole by treating DMF and POCl3. On the other hand, some substituted pyrazole can be converted to pyrazolo[4,3‐c]cinnoline and pyrazolo[4,3‐c]quinoline.
Organic and Biomolecular Chemistry, 2012
European Journal of Organic Chemistry, Apr 1, 2009
ABSTRACT The reaction of aldehydes with allyltrimethylsilane in arene solvents gives symmetrical ... more ABSTRACT The reaction of aldehydes with allyltrimethylsilane in arene solvents gives symmetrical 2,6-disubstituted-4-aryltetrahydropyrans in good yields. The reaction is highly stereoselective. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
The Journal of Organic Chemistry, 2017
Bismuth trifluoromethanesulfonate (Bi(OTf)3) can be efficiently used for the preparation of dihyd... more Bismuth trifluoromethanesulfonate (Bi(OTf)3) can be efficiently used for the preparation of dihydropyrans from β-allenols and aldehydes by oxonium-ene reaction in good yields. The reaction is highly regioselective. On the other hand, the same reaction with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at-45 o C affords hexahydropyrano[4,3b]pyran skeleton in moderate yields.
Synlett, Jul 8, 2022
A variety of oxygen, nitrogen and sulfur heterocyclic compounds are synthesized via one-pot multi... more A variety of oxygen, nitrogen and sulfur heterocyclic compounds are synthesized via one-pot multicomponent Prins, aza-Prins, thia-Prins, oxonium-ene, iminium-ene and thionium-ene cyclization reactions. The reactions proceeds with high diastereo- and regioselectivity. Importantly, C–C, C–N, C–O and C–S bonds are formed in a singsle step. These procedures are extended for the synthesis of biologically active molecules and natural products.1 Introduction2 Prins Cyclization Reactions3 Oxonium-Ene Cyclization Reactions4 Conclusion
The Journal of Organic Chemistry, 2001
It was observed that the reaction of CFCl3 with thiophenoxide gave only 10% of the corresponding ... more It was observed that the reaction of CFCl3 with thiophenoxide gave only 10% of the corresponding thioether. On the other hand, these thioethers could be prepared in excellent yield from diaryl disulfides and CFCl3 in the presence of sodium hydroxymethanesulfinate in aqueous DMF at 4 atm pressure of nitrogen. Dechlorination of the thioether (PhSCFCl2) with different reducing agents were studied. Most of the reducing agents eliminated both fluorine and chlorine functionalities or gave the hydrolyzed products. But its sulfone on treatment with Zinc in methanol gave monochlorofluoromethyl and fluoromethyl phenyl sulfone in good yields. Darzens reaction of these compounds was also studied.
Chemical Communications
A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazoli... more A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent...
Journal of Organic Chemistry, Aug 31, 2021
An efficient methodology has been developed for the synthesis of tetra- and pentasubstituted pyrr... more An efficient methodology has been developed for the synthesis of tetra- and pentasubstituted pyrroles via oxidative self-dimerization of N-propargylamines catalyzed by silver benzoate in the presence of K2S2O8 in good yields. The protocol provides a simple route for the synthesis of both tetra- and pentasubstituted pyrroles with two carbonyl groups in the side chain. The methodology can be extended toward the synthesis of pyrrolo[3,4-d]pyridazine.
ChemInform, Aug 12, 2010
A Novel Synthesis of Oxabicyclo[3.3.1]nonanone via (3,5)-Oxonium-Ene Reaction.-Higher yields are ... more A Novel Synthesis of Oxabicyclo[3.3.1]nonanone via (3,5)-Oxonium-Ene Reaction.-Higher yields are obtained when aliphatic aldehydes are used compared with the aromatic ones [cf. (III)]. The same type of products are constructed by using the epoxide substrates instead of aldehydes [cf.
Journal of Organic Chemistry, Jul 21, 2023
Journal of Organic Chemistry, Feb 22, 2023
ACS omega, Jan 18, 2018
Indium(III) chloride can be efficiently used for the synthesis of 4-vinylpyrrolidine from N-tethe... more Indium(III) chloride can be efficiently used for the synthesis of 4-vinylpyrrolidine from N-tethered alkynealkenol in good yields. The reaction is highly stereo-and regioselective.
Organic and Biomolecular Chemistry, 2021
A simple methodology for the regioselective synthesis of substituted dibenzocyclohepta[1,2-a]naph... more A simple methodology for the regioselective synthesis of substituted dibenzocyclohepta[1,2-a]naphthalenes from phenylacetaldehydes and ortho-alkynyl benzyl alcohols in the presence of a Lewis acid has been developed.
Asian Journal of Organic Chemistry, Jul 7, 2017
A simple and efficient approach has been developed for the synthesis of benzo[1,4]oxazepino-fused... more A simple and efficient approach has been developed for the synthesis of benzo[1,4]oxazepino-fused tetrahydroisoquinoline and tetrahydro-β-carboline derivatives via one-pot cascade reaction sequence. This reaction involves the intramolecular Pictet-Spengler reaction of cyclic iminium ions, which were generated in situ via trifluoroacetic acid (TFA) mediated deprotection of acetal derived from β-arylethylamines and 2-(2,2-diethoxyethoxy)benzaldehyde. All reactions produced a novel library of complex fused polyheterocyclic compounds in good to excellent yields.
Journal of Organic Chemistry, Sep 10, 2014
Indium triflate can be efficiently used for Prins cyclization of acrylyl enol ethers to give tetr... more Indium triflate can be efficiently used for Prins cyclization of acrylyl enol ethers to give tetrahydrofuran ring stereoand regioselectively in good yields. The formation of five-membered rings is against the Baldwin's rule.
ChemInform, Jun 24, 2010
Titanium Tetrafluoride: An Efficient Lewis Acid and Fluorinating Agent for Stereoselective Synthe... more Titanium Tetrafluoride: An Efficient Lewis Acid and Fluorinating Agent for Stereoselective Synthesis of 4-Fluorotetrahydropyran.-Titanium tetrafluoride efficiently promotes the stereoselective formation of 4-fluoropyrans via Prins cyclization. The method is general and can be used both for aldehydes and ketones. The conformations of the di-and tri-substituted tetrahydropyrans are proved by NOE experiments and X-ray analysis. A brief discussion of the mechanism is given as well.
ChemInform, Jun 7, 2010
w-Nitro ketoaliphatic compounds 3a and 3b, prepared by a new and efficient route, have been elabo... more w-Nitro ketoaliphatic compounds 3a and 3b, prepared by a new and efficient route, have been elaborated to short syntheses of both 2,7-dimethyl-1,6-dioxaspiro[4.6]undecane, [(2S,5R,7S)-1a] and 2,7-diethyl-1,6-dioxaspiro[4.6]undecane [(2S,5R,7S)-1b], the pheromones produced by Andrena haemorrhoa and Andrena wilkella, respectively.
Synlett, 2012
The reaction of aldehyde with allylsilane in acetonitrile mediated by boron trifluoride etherate ... more The reaction of aldehyde with allylsilane in acetonitrile mediated by boron trifluoride etherate generated 4-aminotetrahydropyrans in good yields. The product is highly stereoselective. Multicomponent reactions are gaining interest in organic synthesis due to its ability to form multiple bonds in a single step. 1 Substituted tetrahydropyrans are important targets because of their presence in many natural products. 2 These tetrahydropyrans are prepared by hetero-Diels-Alder methods, 3 manipulation of carbohydrates, 4 Prins cyclization, 5 and intramolecular Michael reactions. 6 Although there are a few methods for the synthesis of 4-halo-, 7 4-thio-, 8 4-azido-, 9 4-aryl-, 10 and 4-hydroxytetrahydropyran, 5e,f,7d,11 methods for the synthesis of 4-aminotetrahydropyran are limited. 12 In this paper, an efficient method for the synthesis of 4 aminotetrahydropyran from aldehyde, trimethylallylsilane, and acetonitrile mediated by BF 3 ‚ Et 2 O is disclosed (Scheme 1). Thus, when benzaldehyde was subjected to react with allyltrimethylsilane in acetonitrile in the presence of boron trifluoride etherate, 4-acetamido-2,6-diphenyltetrahydrofuran was obtained in 70% yield.
ChemistrySelect, Jun 1, 2016
Propargyl amine can be efficiently converted to pyrazole N‐oxide from the reaction of sodium nitr... more Propargyl amine can be efficiently converted to pyrazole N‐oxide from the reaction of sodium nitrite in acetic acid catalysed by AgOTf in excellent yields. The pyrazole N‐oxides can be converted into pyrazole by treatment of phosphorous trichloride in refluxing chloroform. The pyrazole N‐oxide could be converted to highly substituted 4‐chloropyrazole by treating DMF and POCl3. On the other hand, some substituted pyrazole can be converted to pyrazolo[4,3‐c]cinnoline and pyrazolo[4,3‐c]quinoline.
Organic and Biomolecular Chemistry, 2012
European Journal of Organic Chemistry, Apr 1, 2009
ABSTRACT The reaction of aldehydes with allyltrimethylsilane in arene solvents gives symmetrical ... more ABSTRACT The reaction of aldehydes with allyltrimethylsilane in arene solvents gives symmetrical 2,6-disubstituted-4-aryltetrahydropyrans in good yields. The reaction is highly stereoselective. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)