Imidazole, oxazole and thiazole alkaloids

Iodine-catalyzed oxidative annulation of 3-cyanoacetylindoles with benzylamines: facile access to 5-(3-indolyl)oxazoles

An iodine-catalyzed oxidative annulation of 3-cyanoacetylindoles with benzylamines has been developed. This reaction enables the convenient synthesis of a variety of 5-(3-indolyl)oxazoles under mild conditions with broad functional group compatibility.

Metal-free iodine(iii)-promoted synthesis of 2,5-diaryloxazoles

A nonmetal-catalyzed oxidative cyclization to achieve 2,5-disubstituted oxazoles from inexpensive and readily available substituted chalcone, (diacetoxyiodo)benzene (PIDA) and ammonium acetate (NH4OAc) at room temperature is described. The reaction forms a variety of 2,5-diaryloxazoles in good to excellent yields with broad substrate scope under mild conditions without the requirement of ligands and additional bases.

Oxazole and thiazole analogs of sulindac for cancer prevention

Aim:

Experimental and epidemiological studies and clinical trials suggest that nonsteroidal anti-inflammatory drugs possess antitumor potential. Sulindac, a widely used nonsteroidal anti-inflammatory drug, can prevent adenomatous colorectal polyps and colon cancer, especially in patients with familial adenomatous polyposis. Sulindac sulfide amide (SSA) is an amide-linked sulindac sulfide analog that showed in vivo antitumor activity in a human colon tumor xenograft model.

Results/methodology:

A new analog series with heterocyclic rings such as oxazole or thiazole at the C-2 position of sulindac was prepared and screened against prostate, colon and breast cancer cell lines to probe the effect of these novel substitutions on the activity of sulindac analogs.

Conclusion:

In general, replacement of the amide function of SSA analogs had a negative impact on the cell lines tested. A small number of hits incorporating rigid oxazole or thiazole groups in the sulindac scaffold in place of the amide linkage show comparable activity to our lead agent SSA.

Catalyst-controlled synthesis of 4-amino-isoquinolin-1(2H)-one and oxazole derivatives

A facile synthetic method for the preparation of oxazole and 4-amino-isoquinolin-1(2H)-one derivatives has been developed from the reaction of N-(pivaloyloxy)-amides and ynamides by using different metal catalysts.

Multicomponent reactions: a sustainable tool to 1,2- and 1,3-azoles

The present review outlines the recent advancements and pioneering efforts on the synthesis of 1,2/1,3-azoles employing a multicomponent strategy.

Conformational Heterogeneity and the Role of the C(2)-H Donor in Mono- and Dihydrated Clusters of Benzoxazole

The significance of the heteroatom in influencing the acidity and binding affinity of the C(2)-H donor in five-membered heterocyclic rings is explored. The water clusters of benzoxazole (BOX) are studied in a supersonic jet by IR-UV double resonance spectroscopy and compared with those of benzimidazole (BIM) and its N-methyl derivative (MBIM). Two conformers are identified for the monohydrated cluster, both of which are O-H···N bound and differ in their orientation with respect to the intermolecular hydrogen bond. IR spectroscopy of the doubly hydrated cluster shows the presence of an intensity enhanced C(2)-H (carbon atom between the heteroatoms in the five-membered ring) stretching mode in addition to two red-shifted bound OH stretches, indicating that the water molecules form a hydrogen-bonded bridge encompassing the N acceptor and the weakly activated C(2)-H bond in oxazole. Comparison of the topological parameters of electron density, natural bond orbital analyses, and computed binding energies of the analogous hydrated structures of BOX, BIM, and MBIM indicates that the C(2)-H bond in the former is a more potent H-bond donor.

Synthesis and fungicidal activity of 3,4-dichloroisothiazole based strobilurins as potent fungicide candidates

A series of 3,4-dichloroisothiazole based novel strobilurin analogs were synthesized, the compound8dwas discovered as a new fungicidal candidate with better efficacy than commercial standards.

I2/TBPB mediated oxidative reaction of aryl acetaldehydes with amidines: synthesis of 1,2,5-triaryl-1H-imidazoles

A direct method for the synthesis of 1,2,5-triaryl-1H-imidazoles was achieved from acetaldehydes with amidines catalyzed by I₂. Various substituted groups can be employed, and this reaction proceeds smoothly in moderate to good yields.

Readily switchable one-pot 5-exo-dig cyclization using a palladium catalyst

A convenient, ligand-free, Pd(OAc)₂-catalyzed one-pot reaction has been developed for the synthesis of oxazolines and oxazoles from easily available acid chlorides and propargylamine.

Rhodium-catalyzed denitrogenative transannulation of 1,2,3-triazolyl-carbamates: efficient access to 4-aminooxazolidinones

The rhodium(ii)-catalyzed denitrogenative transannulation reaction of 1,2,3-triazolyl-carbamates was described providing an efficient access to biologically interesting 4-aminooxazolidinones in excellent yields and selectivities.

One-Pot Synthesis of 2,4,5-Trisubstituted Imidazoles via [2 + 2 + 1] Cycloannulation of 1,3-Bishet(aryl)-monothio-1,3-diketones, α-Substituted Methylamines and Sodium Nitrite through α-Nitrosation of Enaminones

An efficient one-pot synthesis of a series of diversely functionalized trisubstituted 4(5)het(aroyl)-2,5(4)-het(aryl)/alkylimidazoles from readily available 1,3-bishet(aryl)monothio-1,3-diketones has been reported. This novel sequential one-pot, three step protocol, wherein three new carbon nitrogen bonds are formed in contiguous fashion, involves in situ generation of enaminones by reaction of monothio-1,3-diketones with α-substituted methylamines, followed by their α-nitrosation with sodium nitrite and subsequent base mediated intramolecular heterocyclization of the resulting α-hydroxyiminoimines to trisubstituted imidazoles in high yields under mild conditions. These newly prepared 4(5)-het(aroyl)-5(4)-het(aryl)/alkylimidazoles are shown to exist as tautomeric mixture, however, their subsequent alkylation with methyl iodide in the presence of potassium carbonate affords 1-N-methy-2,5-bishet(aryl)-4-het(aroyl)imidazoles in highly regioselective fashion in most of the cases. Synthesis of few 4(5)-(2-hydroxyphenyl)-2,5(4)-substituted imidazoles, which are known to be good coordinating ligands, has also been reported. A probable mechanism for the formation of these imidazoles from hydroxyiminoimine intermediates has also been suggested.

Pd(ii)-catalyzed intramolecular oxidative Heck dearomative reaction: approach to thiazole-fused pyrrolidinones with a C2-azaquarternary center

A Pd(ii)-catalyzed intramolecular oxidative Heck dearomative reaction for the construction of thiazole-fused pyrrolidinones was achieved for the first time.

Visible-light-induced photocatalytic oxytrifluoromethylation of N-allylamides for the synthesis of CF3-containing oxazolines and benzoxazines

A visible-light-induced photocatalytic oxytrifluoromethylation reaction of N-allylamides has been developed for the efficient synthesis of CF3-containing oxazolines and benzoxazines under mild reaction conditions.

Gold-catalyzed tandem reactions of amide-aldehyde-alkyne coupling and cyclization-synthesis of 2,4,5-trisubstituted oxazoles

We report the first cationic gold(i)-catalyzed one-pot reaction of amide, alkyne and aldehyde followed by cyclization, to successfully access highly substituted oxazoles derivatives in good yields. A single catalyst allows the occurring of this multi-step reaction atom- and step-economically, with water as the only theoretical side product.

A facile synthesis of 2,5-disubstituted oxazoles via a copper-catalyzed cascade reaction of alkenes with azides

A novel approach to the synthesis of 2,5-disubstituted oxazoles is developed via a 1,3-dipolar cycloaddition/ring cleavage/1,2-H migration/denitrogenation/copper-catalyzed aerobic oxidative dehydrogenative cyclization cascade.

Copper-catalyzed oxidative coupling reaction of α,β-unsaturated aldehydes with amidines: synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes

A convenient synthesis of 1,2,4-trisubstituted-1H-imidazole-5-carbaldehydes was developed, which features high atom economy, cheap catalysts and mild conditions.

Synthesis of substituted oxazoles from enamides

2,5- and 2,4,5-substituted oxazoles were prepared in one-pot by the NBS/Me₂S-mediated cyclization of enamides in the presence of base.