Fluorous Synthesis of Hydantoin-, Piperazinedione-, and Benzodiazepinedione-Fused Tricyclic and Tetracyclic Ring Systems

An Old Story in the Parallel Synthesis World: An Approach to Hydantoin Libraries

An approach to the parallel synthesis of hydantoin libraries by reaction of in situ generated 2,2,2-trifluoroethylcarbamates and α-amino esters was developed. To demonstrate utility of the method, a library of 1158 hydantoins designed according to the lead-likeness criteria (MW 200-350, cLogP 1-3) was prepared. The success rate of the method was analyzed as a function of physicochemical parameters of the products, and it was found that the method can be considered as a tool for lead-oriented synthesis. A hydantoin-bearing submicromolar primary hit acting as an Aurora kinase A inhibitor was discovered with a combination of rational design, parallel synthesis using the procedures developed, in silico and in vitro screenings.

Stereoselective synthesis of fused tetrahydroquinazolines through one-pot double [3 + 2] dipolar cycloadditions followed by [5 + 1] annulation

The one-pot [3 + 2] cycloaddition of an azomethine ylide with a maleimide followed by another [3 + 2] cycloaddition of an azide with the second maleimide gives a 1,5-diamino intermediate which is used for a sequential aminomethylation reaction with formaldehyde through [5 + 1] annulation to afford a novel polycyclic scaffold bearing tetrahydroquinazoline, pyrrolidine, pyrrolidinedione, and N-substituted maleimide in stereoselective fashion.

Sequential [3 + 2] and [4 + 2] cycloadditions for stereoselective synthesis of a novel polyheterocyclic scaffold

A strategy of combining [3 + 2] cycloaddition and intramolecular Diels-Alder reaction is developed for the synthesis of a novel polycyclic scaffold with skeletal and substitutional diversities. Intermediates generated from stereoselective [3 + 2] cycloaddition of azomethine ylides and maleimides were derivatized for intramolecular Diels-Alder reaction of furan to form highly condensed heterocyclic products as racemic single diastereomers.

Morita–Baylis–Hillman adducts as effective dipolarophiles in Copper(i)-catalyzed 1,3-dipolar cycloaddition with azomethine ylides: asymmetric construction of pyrrolidine derivatives containing quaternary stereogenic center

The first catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides with easily accessible MBH adducts as the dipolarophiles has been developed successfully.

Aryl-Csp(3) bond rotation barriers of 2-aryl perhydropyrrolo[3,4-c]pyrrole-1,3-diones

The static and dynamic features of 2-aryl perhydropyrrolo[3,4-c]pyrrole-1,3-diones bearing N-acyl substituents have been assessed with the aid of crystal structures and VT NMR spectra. Rotation barriers for the aryl-Csp(3) bonds in these molecules show surprising variation. Amide-substituted derivatives and fused piperazinediones (six-membered fusion) exhibit very substantial barriers of 14-15 kcal/mol. Fused benzodiazepinediones (seven-membered fusion) have lower but still significant barriers (10 kcal/mol), while fused hydantoins (five-membered fusion) have barriers that are too low to measure by VT NMR (< or =10 kcal/mol). A rationale for the origin of the barriers is presented.

Fluorous parallel synthesis of a piperazinedione-fused tricyclic compound library

A fluorous-linker-assisted solution-phase protocol has been developed and applied to parallel synthesis of a piperazinedione-fused tricyclic compound library. The one-pot [3 + 2] cycloaddition of fluorous amino esters, aldehydes, and maleimides afforded bicyclic proline derivatives. The intermediates were subjected to N-acylation with chloroacetyl chloride, followed by displacement reactions with amines. Linker cleavage with concomitant lactamization yielded the final products. Microwave heating was employed to facilitate several reaction steps and fluorous solid phase extraction (F-SPE) was employed to purify the intermediates. During the method development, a small library containing sixteen analogs was prepared. The optimized conditions were applied to the synthesis of a production library containing ninety analogs.

Fluorous-enhanced multicomponent reactions for making drug-like library scaffolds

Multicomponent reactions (MCRs) generate multiple bonds in a single reaction process, which is highly efficient to construct relatively complex molecules. Conducting post-MCR modification reactions further increases the molecular complexity and diversity. MCR has become a powerful approach to make drug-like molecules in lead generation chemistry. In fluorous MCR (F-MCR), one of the starting materials is attached to a fluorous tag and used as the limiting agent. After the MCR, the fluorous component is fished out from the reaction mixture and used for post-MCR modifications. The fluorous tag can be finally removed in traceless fashion by displacement or cyclization reactions. Unique fluorous technology such as fluorous solid-phase extraction (F-SPE) facilitates the separation process. Other techniques such as microwave irradiation and plate-to-plate SPE can also be used to make the F-MCR even more efficient. Syntheses of unique heterocyclic and natural product-like library scaffolds using Ugi/de-Boc/cyclization, MCR/Suzuki coupling, and [3+2] cycloaddition/de-tag/cyclization protocols are described in this paper.

Fluorous synthesis of sclerotigenin-type benzodiazepine-quinazolinones

A new synthetic protocol for sclerotigenin-type benzodiazepine-quinazolinone library scaffold is introduced. A fluorous benzyl protecting group is used for synthesis of 4-benzodiazepine-2,5-dione intermediate and also as a phase tag for fluorous solid-phase extraction (F-SPE).

A recyclable fluorous organocatalyst for Diels-Alder reactions

Chiral fluorous imidazolidinone catalyst 2 provides consistently high enantioselectivities in Diels-Alder reactions of dienes and alpha, beta-unsaturated aldehydes. The catalyst can be readily separated from the reaction products by fluorous solid-phase extraction, and recovered in excellent purity for direct reuse.

Microwave-Enhanced High-Speed Fluorous Synthesis

Increasing reaction speed and simplifying product purification are two major ways to improve the efficiency of organic synthesis. A new technology for high-speed solution-phase synthesis has been developed by combination of microwave heating and fluorous purification. This review describes different techniques for microwave-enhanced fluorous synthesis and their applications in Pd-catalyzed cross-coupling reactions, free-radical reactions, multicomponent reactions, and compound library synthesis.