The N-sulfonyl spiroaziridine oxindole is a recently developed versetile precusor in synthesis of... more The N-sulfonyl spiroaziridine oxindole is a recently developed versetile precusor in synthesis of wide range of 3,3-disubstitued/spirooxindoles. It usually prepared in three steps from isatin and needs costly and limited available sulfinimides and hazardous peracid. A sequential and one-pot direct strategy for the synthesis of terminal N-sulfonyl spiroaziridine oxindole has been developed under ambient conditions with excellent yields (up to 95%) from easily accessible spiroepoxy oxindoles by regioselective ammination with aqueous ammonia and subsequent ring enclosure reaction of resulting 1,2-amino alcohol using easily available sulfonyl chloride and base. Other salient features of the protocol include inexpensive substrate requirement and ease of isolation of the desired product by performing single column chromatographic purification after two consecutive steps.
We synthesized 4-bromo-3-formyl-N-phenyl-5-propylthiophene-2-carboxamide by using three successiv... more We synthesized 4-bromo-3-formyl-N-phenyl-5-propylthiophene-2-carboxamide by using three successive direct lithiations and a bromination reaction starting from thiophene. All these lithiation reactions were carried out at −78 °C to RT over a period of 1 to 24 h based on the reactivity of electrophile. This is a four-step protocol starting from thiophene with an overall yield of 47%.
5-propyl-2-((trityloxy)methyl)thiophene-3-carbaldehyde was synthesized by using the concept of ch... more 5-propyl-2-((trityloxy)methyl)thiophene-3-carbaldehyde was synthesized by using the concept of chemo- and regioselective Br/Li exchange reaction from 3-bromo-5-propyl-2-((trityloxy)methyl)thiophene. This is a five-step protocol starting from thiophene with an overall yield of 33%. These lithium/halogen exchange reactions were carried out at −78 °C to rt over the period of 1 to 18 h depending on the reactivity of electrophiles.
Umpolung alkylation of Evans' auxiliary substituted β-ketoimides affords the diastereomerical... more Umpolung alkylation of Evans' auxiliary substituted β-ketoimides affords the diastereomerically pure products in yields ranging from 40 to 80%. The reaction itself proceeds with diastereoselectivities between 3 : 1 and 18 : 1. Dialkylzinc serves as the nucleophile and umpolung of the β-keto-imide enolate is achieved by the action of Koser's reagent.
A-86929, a dopamine D1 agonist was synthesized with 95% ee in five steps with overall yield of 56... more A-86929, a dopamine D1 agonist was synthesized with 95% ee in five steps with overall yield of 56% via catalytic enantioselective one-pot aziridination followed by Friedel-Crafts cyclization and a mild Pictet-Spengler cyclization protocol.
The N-sulfonyl spiroaziridine oxindole is a recently developed versetile precusor in synthesis of... more The N-sulfonyl spiroaziridine oxindole is a recently developed versetile precusor in synthesis of wide range of 3,3-disubstitued/spirooxindoles. It usually prepared in three steps from isatin and needs costly and limited available sulfinimides and hazardous peracid. A sequential and one-pot direct strategy for the synthesis of terminal N-sulfonyl spiroaziridine oxindole has been developed under ambient conditions with excellent yields (up to 95%) from easily accessible spiroepoxy oxindoles by regioselective ammination with aqueous ammonia and subsequent ring enclosure reaction of resulting 1,2-amino alcohol using easily available sulfonyl chloride and base. Other salient features of the protocol include inexpensive substrate requirement and ease of isolation of the desired product by performing single column chromatographic purification after two consecutive steps.
We synthesized 4-bromo-3-formyl-N-phenyl-5-propylthiophene-2-carboxamide by using three successiv... more We synthesized 4-bromo-3-formyl-N-phenyl-5-propylthiophene-2-carboxamide by using three successive direct lithiations and a bromination reaction starting from thiophene. All these lithiation reactions were carried out at −78 °C to RT over a period of 1 to 24 h based on the reactivity of electrophile. This is a four-step protocol starting from thiophene with an overall yield of 47%.
5-propyl-2-((trityloxy)methyl)thiophene-3-carbaldehyde was synthesized by using the concept of ch... more 5-propyl-2-((trityloxy)methyl)thiophene-3-carbaldehyde was synthesized by using the concept of chemo- and regioselective Br/Li exchange reaction from 3-bromo-5-propyl-2-((trityloxy)methyl)thiophene. This is a five-step protocol starting from thiophene with an overall yield of 33%. These lithium/halogen exchange reactions were carried out at −78 °C to rt over the period of 1 to 18 h depending on the reactivity of electrophiles.
Umpolung alkylation of Evans' auxiliary substituted β-ketoimides affords the diastereomerical... more Umpolung alkylation of Evans' auxiliary substituted β-ketoimides affords the diastereomerically pure products in yields ranging from 40 to 80%. The reaction itself proceeds with diastereoselectivities between 3 : 1 and 18 : 1. Dialkylzinc serves as the nucleophile and umpolung of the β-keto-imide enolate is achieved by the action of Koser's reagent.
A-86929, a dopamine D1 agonist was synthesized with 95% ee in five steps with overall yield of 56... more A-86929, a dopamine D1 agonist was synthesized with 95% ee in five steps with overall yield of 56% via catalytic enantioselective one-pot aziridination followed by Friedel-Crafts cyclization and a mild Pictet-Spengler cyclization protocol.
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