Browsing by Author "Thikekar, Tushar Ulhas"

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Base Controlled Three-Component Regioselective Synthesis of 2-Imino Thiazolines and 2-Thioxoimidazolin-4-ones
(2019-04-01)
Barve, Indrajeet J.
;
Chang, Wong-Jin
;
Lin, Yen-Tzu
;
Thikekar, Tushar Ulhas
;
Sun, Chung-Ming
Base-controlled regioselective synthesis of 2-imino thiazolines and 2-thioxoimidazolin-4-ones was achieved to use a one-pot reaction between chiral amino esters, isothiocyanates, and alpha-bromoketones/alkyl halides. This three-component coupling reaction in acetonitrile provides 2-imino thiazolines, whereas the formation of 2-thioxoimidazolin-4-ones was observed under basic conditions at ambient temperature. The corresponding products were obtained in good to excellent yield with broad substrate scope. Isolation of thiourea and thiohydantoin intermediates disclosed the course of the reaction mechanism.
Design, synthesis and diversification of natural product-inspired hydantoin-fused tetrahydroazepino indoles
(2015-01-01)
Barve, Indrajeet J.
;
Dalvi, Prashant B.
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Thikekar, Tushar Ulhas
;
Chanda, Kaushik
;
Liu, Yu-Li
A facile and efficient synthesis of novel oxo, thio and seleno hydantoin fused tetrahydroazepino [4,5-b] indoles was reported. A naturally occurring iboga class alkaloid inspired seven-membered azepino[4,5-b] indole ring was synthesized as a new scaffold through Pictet-Spengler reaction followed by skeletal rearrangement of the aziridine ring. To improve the efficiency of the synthetic route, the double bond of the rearranged olefinic product 5 was reduced and a privileged hydantoin moiety was constructed on the core system through urea formation using a variety of isocyanates, isothiocyanates and isoselenocyanates followed by intramolecular cyclization to incorporate elements of diversity. The regeneration of the double bond of intermediate 9 afforded hydantoin-fused tetrahydroazepino [4,5-b] indoles.
Palladium-Catalyzed Regioselective Synthesis of 1,2-Fused Indole-Diazepines via [5+2] Annulation of o-Indoloanilines with Alkynes
(2017-10-04)
Thikekar, Tushar Ulhas
;
Sun, Chung-Ming
;
應用化學系
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Department of Applied Chemistry
An efficient and regioselective palladium(II)-catalyzed [5+2] annulation of unprotected o-indoloanilines with internal alkynes under microwave irradiation has been explored. The diverse imine-containing 1,2-fused indole[1,7-a]diazepines are constructed in moderate to excellent yields. The mechanistic pathway shows pivalic acid and molecular oxygen to play crucial roles for the regeneration of highly active electrophilic palladium species in the catalytic cycle.
Silver(I)-Catalyzed Regioselective Synthesis of Triazole Fused-1,5-Benzoxazocinones
(2017-05-05)
Barve, Indrajeet J.
;
Thikekar, Tushar Ulhas
;
Sun, Chung-Ming
;
應用化學系
;
Department of Applied Chemistry
An efficient and regioselective synthesis of novel 1,2,3-triazole-fused-1,5-benzoxazocinones through intramolecular cyclization of substituted ethynyl triazoyl benzoic acids was explored. A crucial precursor 5-iodo-1,2,3-triazole benzoate was obtained from substituted 2-azido benzoic acid esters in a single step through a Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) reaction using a CuI/NBS catalytic system. A carbon carbon triple bond was installed through a Sonogashira coupling reaction by various terminal alkynes. Finally, the 1,4,5-substituted ethynyl triazoyl benzoic acids were cyclized by a AgOTf-mediated intramolecular cyclization to afford 8-endo-dig 1,2,3-triazole-fused-1,5-benzoxazocinones exclusively.
Skeletally Diverse Synthesis of Indole-Fused Diazocine and Diazepine Frameworks by One-Pot, Two-Component Cascade Reaction
(2016-01-15)
Thikekar, Tushar Ulhas
;
Selvaraju, Manikandan
;
Sun, Chung-Ming
;
應用化學系
;
Department of Applied Chemistry
An expeditious and novel strategy has been explored for the synthesis of structurally diverse indole-fused diazocine and diazepine derivatives. A substrate-based diversification approach of methyl-3-aminoindole/indoline benzoates coupled with the Pictet-Spengler reaction and three different reaction cascades furnished indolodiazepine and indoloquinoxalines. The formation of indolodiazocines proceeds through an initial condensation followed by intramolecular alkylation.