Zhaopeng Liu

N-Fluoro-3-ethyl-3-methyl-1,1-dioxo-2,3-dihydro-1H-1λ6-benzo[e]1,2-thiazin-4-one, a new and efficient agent for electrophilic fluorination of carbanions

Abstract N-Fluoro-3-ethyl-3-methyl-1,1-dioxo-2,3-dihydro-1H-1λ6-benzo[e]1,2-thiazin-4-one (1) was prepared in good yield by fluorination of the corresponding sultam (3) with FClO3. The sultam (3) was prepared from saccharin (2) in 3 steps. The N-fluorosultam (1), a very stable crystalline solid, was found to fluorinate carbanions readily in good to excellent yields.

New Developments in the Synthesis of Saccharin Related Five- and Six-Membered Benzosultams

Recent developments in the novel synthesis of saccharin related five-and six-membered benzosultams are reviewed.

Synthesis of enantiomerically pure (+)- and (-)-3-methyl-3-(2-naphthyl)- 2H-benzo〔e〕〔1,2〕thiazine 1,1,4-triones

Treatment of N-t-butylbenzenesulfonamide with an excess of BuLi, followed by the reaction with methyl 2-naphthylpropanoate, gave the corresponding 2-carboxybenzenesulfonamide, which underwent cyclization under TMSCl-NaI-MeCN reflux conditions to afford the N-sulfonylimine. Bromination of the N-sulfonylimine and ring expansion mediated by 20% KOH (aq.), formed the 3-methyl-3-(2-naphthyl)benzo[e][1,2]thiazine 1,1,4-trione. Optical resolution of the racemic benzosultam using (-)-menthoxyacetyl chloride, furnished the (+)-and (-)-3 -methyl-3-(2-naphthyl)benzo[e][1,2]thiazine 1,1,4-triones.

Novel method for the synthesis of 3-monosubstituted six-membered benzosultams

3-Monosubstituted six-membered benzosultams with a wide range of functional groups were prepared by simple and convenient two-step procedures. o-Lithiation of N-Boc-o-toluenesulfonamide followed by reaction with aldehydes gave carbinol sulfonamides, which were converted to 3-monosubstituted six-membered benzosultams via TMSCl/NaI/MeCN reagent mediated cyclization. The mechanism and the scope of this novel transformation are studied.

A Novel Synthetic Approach to Benzo[d]isothiazole 1,1‐Diones Having a Secondary Alkyl Substituent at the 3‐Position

Abstract A novel method for the synthesis of benzo[d]isothiazole 1,1‐diones with a secondary alkyl substituent at the 3‐position is described. Treatment of N‐tert‐butylbenzenesulfonamide (1) with an excess of BuLi, followed by the reaction with methyl 2‐arylpropanoate, gave the corresponding ortho‐functionalized benzenesulfonamides 2a–d, which underwent cyclization under TMSCl–NaI–MeCN reflux conditions to afford 3‐substituted benzo[d]isothiazole 1,1‐diones 3a–d.

Facile synthesis of disubstituted and spiro five-membered benzosultams mediated by TMSCl–NaI–MeCN reagent

o-Lithiation of N-tert-butylbenzenesulfonamide followed by reaction with ketones gave carbinol sulfonamides, which underwent TMSCl–NaI–MeCN reagent mediated cyclization to afford 3,3-disubstituted and spiro-2,3-dihydrobenzo[d]isothiazole-1,1-diones in high yields.

IODOTRIMETHYLSILANE AND CATALYTIC IODINE PROMOTED CYCLIZATION FOR THE FACILE SYNTHESIS OF 3-MONOARYLATED FIVE-MEMBERED BENZOSULTAMS

3-Monoarylated five-membered benzosultams with various functional groups were prepared by simple and convenient two-step procedures. N t-Bu-benzenesulfonamides were lithiated and reacted with substituted aromatic aldehydes to form the corresponding carbinols, which were converted to the cyclic compounds via a sequence of consecutive processes mediated by TMSC1-Nal-MeCN reagent and catalytic amount of iodine. Iodine played a crucial role in the eliminating the reductive side reaction in the cyclization processes.