Duddu S. Sharada

Applications of Baylis–Hillman chemistry: one-pot convenient synthesis of functionalized (1H)-quinol-2-ones and quinolines

A simple synthesis of functionalized (1H)-quinol-2-ones and quinolines from the Baylis-Hillman adducts, i.e. alkyl 3-hydroxy-2-methylene-3-arylpropanoates and β-hydroxy-a-methylene-β-arylalkanones, respectively, has been described.

Baylis-Hillman chemistry: a novel synthesis of functionalized 1,4-pentadienes

Abstract A novel synthesis of functionalized 1,4-pentadienes via the reaction of acrylonitrile with allyl halides, derived from Baylis–Hillman adducts, in the presence of DABCO has been described, demonstrating for the first time the application of allyl halides as electrophiles in the Baylis–Hillman reaction.

Applications of Baylis-Hillman chemistry: enantioselective synthesis of (-)-methyl 3-aryl-2-methylene-3-(prop-2-yn-1-yloxy)propanoates via chiral leaving group strategy

Abstract Asymmetric synthesis of (−)-methyl 3-aryl-2-methylene-3-(prop-2-yn-1-yloxy)propanoates in 25–40% enantiomeric purities via the reaction of methyl (2 Z )-3-aryl-2-(bromomethyl)prop-2-enoates with prop-2-yn-1-ol in the presence of quinidine is described.

C(sp2)–H Functionalization of 2H-Indazoles at C3-Position via Palladium(II)-Catalyzed Isocyanide Insertion Strategy Leading to Diverse Heterocycles

Herein, we have reported an efficient Pd-catalyzed C-H functionalization of 2H-indazole at C3-position via an isocyanide insertion strategy for the synthesis of unprecedented benzoxazinoindazoles, indazoloquinaoxalines and benzoxazinoindazolones for the first time. Our new method provides an operationally simple and versatile route for a selective synthesis of 2-(2H-indazol-2-yl)phenols. Furthermore, we developed a sequential one-pot strategy for the synthesis of benzoxazinoindazolone under metal-oxidant-free conditions. We also achieved the isocyanide insertion between C(sp(2))-H and oxygen heteroatom for the first time. The key features of the present protocol are construction of 4 bonds in one-pot, synthesis of new skeletally diverse scaffolds, broad substrate scope, high yields and environmentally benign conditions.

Scaffold Diversity through a Branching Double-Annulation Cascade Strategy: Iminium-Induced One-Pot Synthesis of Diverse Fused Tetrahydroisoquinoline Scaffolds

A branching double-annulation cascade (BDAC) strategy for diverse and complex fused THIQ scaffolds via a highly reactive iminium-induced one-pot double-cyclization sequence involving Pictect-Spengler-type cyclization has been developed for the first time. The salient features of this protocol are that it allows direct and rapid access to unprecedented diverse fused THIQ skeletons, is metal/catalyst free, has a cleaner reaction profile, provides good to excellent yields, and is a convenient approach. This catalyst-free domino process facilitates the double annulation with a variety of scaffold building agents via two C-N and one C-X (X = C, N, O) bond formation in a single step under uniform reaction conditions. Furthermore, we reveal an unusual dual BDAC sequence leading to N-N-linked isoquinoline dimer.

Nickel-Catalyzed Aerobic Oxidative Isocyanide Insertion: Access to Benzimidazoquinazoline Derivatives via a Sequential Double Annulation Cascade (SDAC) Strategy

An efficient protocol for the synthesis of quinazoline derivatives through nickel-catalyzed ligand-/base-free oxidative isocyanide insertion under aerobic conditions with intramolecular bis-amine nucleophiles has been developed. A one-pot sequential double annulation cascade (SDAC) strategy involving an opening of isatoic anhydride and annulation to benzimidazole and further nickel-catalyzed intramolecular isocyanide insertion has also been demonstrated. The method is operationally simple to implement with a wide variety of substrates and represents a new approach for multiple C-N bond formations. The methodology has been successfully applied to the syntheses of hitherto unreported imidazo-fused benzimidazoquinazolines via a deprotection-GBB reaction sequence. Further, a florescence study reveals the potential of the present strategy for the discovery of highly fluorescent probes.

Synthesis of dipyrrin-containing architectures

Dipyrrins are valuable precursors to dyes [dipyrrinatoboron difluoride, bis(dipyrrinato)-zinc(II) complexes] and serve as ligands in a variety of self-assembled materials. Six new dipyrrin-containing architectures have been synthesized. The architectures include bis(dipyrrinato) complexes containing copper(II) or palladium(II), a dipyrrin bearing a protected phosphonic acid unit, a porphyrin bearing two dipyrrins in a trans configuration, a linear diphenylethyne-linked dipyrromethane-dipyrrin building block, and a triad composed of two zinc porphyrins joined via an intervening bis(dipyrrinato)copper(II) complex. Two porphodimethenatozinc complexes were prepared and found to have Φf ≤ 0.002 (in toluene at room temperature), which is substantially less than the analogous bis(dipyrrinato)zinc complexes. Taken together, the syntheses described herein should broaden access to dipyrrins for use as complexation motifs in supramolecular chemistry and as pigments in light-harvesting applications.

A Direct Cycloaminative Approach to Imidazole Derivatives via Dual C–H Functionalization

Organoiodine(III)-promoted C(sp3)-H azidation was a key step for the cycloaminative process. An unprecedented method for metal-free dehydrogenative N-incorporation into C(sp3)-H and C(sp2)-H bonds for the synthesis of diverse imidazoles has been disclosed. The overall transformation involves the construction of four C-N bonds through hydroamination-azidation-cyclization sequence. The reaction can be easily handled and proceeds under mild conditions. Further, the potential of the present strategy is revealed by the practical synthesis of N-heterocyclic carbene (NHC) precursors.