Dharmendra Kumar Tiwari

Visible‐Light/Photoredox‐Mediated sp3 CH Functionalization and Coupling of Secondary Amines with Vinyl Azides in Flow Microreactors

Structurally diverse imidazole derivatives were synthesized by a visible-light/[Ru(bpy)3 ][(PF6 )2 ]-mediated coupling of vinyl azides and secondary amines in flow microreactors. This operationally simple and atom-economical protocol allows the formation of three new C-N bonds through the functionalization of sp(3)  C-H bonds adjacent to the secondary nitrogen atom. In order to get mechanistic insight of the coupling reaction, several control experiments were carried out and discussed.

Magnetically separable nano-copper catalyzed unprecedented stereoselective synthesis of E-vinyl sulfones from tosylmethyl isocyanide and alkynes: TosMIC as a source of the sulfonyl group

We have developed an unprecedented efficient and mild catalytic route for stereoselective synthesis of E-vinyl sulfones from terminal alkynes and tosylmethyl isocyanide (TosMIC) in the presence of magnetically separable nano-copper (0) stabilized on Fe3O4. A variety of vinyl sulfones were obtained in moderate to good yields. In this newly developed protocol TosMIC acts as a sulfonyl source. The catalyst was magnetically removed and recycled easily five times without any appreciable loss in activity.

Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

Summary The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

Transition-Metal-Free Quinoline Synthesis from Acetophenones and Anthranils via Sequential One-Carbon Homologation/Conjugate Addition/Annulation Cascade

A transition-metal-free method for the construction of functionalized quinolines from readily available acetophenones and anthranils is reported. This one-pot reaction cascade involves in situ generation of α,β-unsaturated ketones from the acetophenone via one-carbon homologation by DMSO followed by the aza-Michael addition of anthranils and subsequent annulation. DMSO acted in this reaction not only as solvent but also as one carbon source, thus providing a highly atom-economical and environmentally benign approach for the synthesis of 3-substituted quinolines.

Magnetically recoverable Cu0/Fe3O4 catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides

An efficient, one pot tandem nano Cu(0)/Fe3O4 catalyzed highly regioselective synthesis of 3-substituted pyrrole-2,4 dicarboxylates from unactivated terminal alkynes and isocyanides has been developed. This strategy exhibits an unprecedented double addition of isocyanides on unactivated terminal alkynes to obtain trisubstituted pyrroles in high yields. Furthermore, the catalyst was magnetically recovered and reused five times without any appreciable loss of activity.

Palladium catalyzed domino reaction of 1,4-disubstituted 1,2,3-triazoles via double C–H functionalization: one-pot synthesis of triazolo[1,5-f]phenanthridines

A palladium catalyzed domino coupling reaction of 1,4-disubstituted triazoles via homocondensation with a second molecule is presented. The domino couplings involve the formation of biaryl and bi(hetero)aryl bonds through a five membered carbopalladacycle intermediate. The approach provides a simple, straight forward and facile route to access triazolo[1,5-f]phenanthridines in high yields. Furthermore, the developed protocol was extended to heterocondensation in the presence of norbornene.

A general and practical route to 4,5-disubstituted oxazoles using acid chlorides and isocyanides

An efficient and mild method for the synthesis of 4,5-disubstituted oxazoles has been developed. A series of 4,5-disubstituted oxazoles were prepared via [3 + 2] cycloaddition reaction of various isocyanides and acid chlorides in the presence of base. This method serves as an efficient preparation of 5-formyloxazole which might prove to be a synthetically useful intermediate.

Transition-Metal-Free Approach for the Synthesis of 4-Aryl-quinolines from Alkynes and Anilines

An efficient and transition-metal-free approach for the synthesis of 4-arylquinolines from readily available anilines and alkynes in the presence of K2S2O8 and DMSO has been developed. A variety of alkynes and anilines having a diverse range of substitution patterns can undergo the one-pot cascade process successfully. Effectively, this method uses DMSO as one carbon source, thus providing a highly atom-economical and environmentally benign approach for the synthesis of 4-arylquinolines.