Nadeem S Sheikh

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The development of photoredox reactions of aryloxy-amides for the generation of amidyl radicals and their use in hydroamination-cyclization and N-arylation reactions is reported. Owing to the ease of single-electron-transfer reduction of the aryloxy-amides, the organic dye eosin Y was used as the photoredox catalyst, which results in fully(More)
The lithiation of N-tert-butoxycarbonyl (N-Boc)-1,2,3,4-tetrahydroisoquinoline was optimized by in situ IR (ReactIR) spectroscopy. Optimum conditions were found by using n-butyllithium in THF at -50 °C for less than 5 min. The intermediate organolithium was quenched with electrophiles to give 1-substituted 1,2,3,4-tetrahydroisoquinolines. Monitoring the(More)
Cyclophanediene dihydropyrenes (CPD-DHP) are photochromic compounds because they change their color by irradiation with lights of different color. Potential use of CPD-DHP photoswitch in memory devices requires a very slow thermal return in the dark in the absence of any side reaction. Herein, thermal return of CPDs to DHPs, and an unwanted sigmatropic(More)
cis-2,5-Disubstituted tetrahydrofurans constitute the core of several natural products and synthetic analogues which exhibit a broad and interesting range of biological activities. This review highlights a personal perspective and provides a comparative note on the synthesis of cis-2,5-disubstituted tetrahydrofuran rings from 1,5-diene precursors using(More)
The permanganate-mediated oxidative cyclization of a series of 2-methylenehept-5-eneoates bearing different chiral auxiliaries was investigated, leading to the discovery of trans-2-tritylcyclohexanol (TTC) as a highly effective chiral controller for the formation of the 2,5-substituted THF diol product with high diastereoselectivity (dr ∼97:3). Chiral(More)
A general and enantioselective synthesis of 2-substituted 2-phenylpyrrolidines and -piperidines, an important class of pharmaceutically relevant compounds that contain a quaternary stereocenter, has been developed. The approach involves lithiation-substitution of enantioenriched N-Boc-2-phenylpyrrolidine or -piperidine (prepared by asymmetric Negishi(More)
A photoinduced cascade strategy leading to a variety of differentially functionalized nitriles and ketones has been developed. These protocols rely on the oxidative generation of iminyl radicals from simple oximes. Radical transposition by sp3-sp3 C-C and sp3 C-H bond cleavages gives access to distal carbon-radicals that undergo SH2-functionalizations.(More)
Proton abstraction of N-tert-butoxycarbonyl-piperidine (N-Boc-piperidine) with sBuLi and TMEDA provides a racemic organolithium that can be resolved using a chiral ligand. The enantiomeric organolithiums can interconvert so that a dynamic resolution occurs. Two mechanisms for promoting enantioselectivity in the products are possible. Slow addition of an(More)
Shown herein is that polyfunctionalized nitrogen heterocycles can be easily prepared by a visible-light-mediated radical cascade process. This divergent strategy features the oxidative generation of iminyl radicals and subsequent cyclization/radical trapping, which allows the effective construction of highly functionalized heterocycles. The reactions(More)
2,5-Disubstituted tetrahydrofurans constitute the core skeleton of several natural products and are pivotal synthetic analogues of medicinal importance that exhibit remarkable bioactivities. Oxasqualenoid natural products are implicated as potent biologically active molecules, particularly with regard to demonstrating significant cytotoxicity.(More)