Two protocols for the combinatorial synthesis of 5-(dialkylamino)tetrazoles were developed. The best success rate (67%) was shown by the method that used primary and secondary amines, 2,2,2-trifluoroethylthiocarbamate, and sodium azide as the starting reagents. The key steps included the formation of unsymmetrical thiourea, subsequent alkylation with 1,3-propane sultone and cyclization with azide anion. A 559-member aminotetrazole library was synthesized by this approach; the overall readily accessible (REAL) chemical space covered by the method exceeded 7 million feasible compounds.

A 1,2,4-triazole motif is present in numerous commercialized and investigational bioactive molecules. Despite its importance for medicinal chemistry, there is a lack of convenient combinatorial approaches toward this molecular core. Herein, we present a synthetic strategy suitable for the quick preparation of a library of structurally diverse 1,2,4-triazoles in a one-pot setting. The key steps include the formation of thioureas followed by S-alkylation using 1,3-propane sultone and consecutive ring closure leading to the desired 1,2,4-triazoles. Parallel synthesis yields thousands of 1,2,4-triazoles in a cost- and time-efficient manner from commercially available chemicals.

The cover picture shows a 2,2,2-trifluoroethyl oxalate derivative utilized by Enamine scientists in a one-pot parallel synthesis of aliphatic oxamides. The developed procedure provides synthetic and medicinal chemists with a facile route to large collections of compounds bearing the oxamide motif. Details are discussed in the article by Y. S. Moroz, P. K. Mykhailiuk et al. on p. 2120 ff. This cover is dedicated to the 25th anniversary of Enamine Ltd.

A simple parallel synthesis approach to unsymmetrical N-1,N-2-substituted aliphatic oxamides using methyl (2,2,2-trifluoroethyl) oxalate and bis(2,2,2-trifluoroethyl) oxalate was developed. The method was validated on a 52-membered set of the oxamides, derived mainly from hindered primary and secondary aliphatic amines, and gave the products with a high overall success rate in moderate yields.

One-pot synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from carboxylic acids and nitriles was optimized to parallel chemistry. The method was validated on a 141 member library; the desired products were recovered with a high success rate and in moderate yields. Practical application of the approach was demonstrated in the synthesis of bioactive compound pifexole and agonists of free fatty acid receptor 1. A library of 4 948 100 synthesizable drug-like 3,5-disubstituted 1,2,4-oxadiazoles was enumerated based on the method and available validated reagents.

Abstract4‐ Mono‐ and disubstituted semicarbazides (III) and (VI) (25 examples) in all are obtained starting from bis(2,2,2‐trifluoroethyl)carbonate or 2,2,2‐trifluoroethylchloroformate and primary and secondary alkyl‐ and arylamines under conditions of parallel synthesis.

A diverse library of twenty-five 4-mono- and disubstituted semicarbazides was prepared in a one-pot two-step approach. The method includes formation of a carbamate from bis(2,2,2-trifluoroethyl)carbonate or 2,2,2-trifluoroethylchloroformate and a primary or secondary amine and subsequent interaction of the carbamate with hydrazine to result in a semicarbazide. The approach allowed to obtain 4-substituted semicarbazides on a large scale in good yield and high purity.

A simple and cost-effective one-pot parallel synthesis approach to sulfides, sulfoxides, and sulfones from thiourea was elaborated. The method combines two procedures optimized to the parallel synthesis conditions: alkylation of thiourea with alkyl chlorides and mono or full oxidation of in situ generated sulfides with H2O2 or H2O2-(NH4)2MoO4. The experimental set up required commonly used lab equipment: conventional oven and ultrasonic bath; the work up includes filtration or extraction with chloroform. The method was evaluated on an 81 member library of drug-like sulfides, sulfoxides, and sulfones yielding the compounds on a 30-300 mg scale. A small-scale synthesis of 2-(benzhydrylsulfinyl)acetamide (modafinil) utilizing our approach resulted in similar efficiency to the published procedures.

A one-pot parallel synthesis of N(1)-aryl-N(2)-alkyl-substituted oxamides with 2,2,2-trifluoroethyl chlorooxoacetate was developed. The synthesis of a library of 45 oxamides revealed higher efficiency of this reagent over the known ethyl chlorooxoacetate. The reagent was successfully used to prepare the known oxamide-containing HIV entry inhibitors.

A combination of a condensation mixture [a Lewis acid, Ti(Oi-Pr)4, and a water scavenger, 1-(trimethylsilyl)-2-pyrrolidinone] and a simple reductant (NaBH4) provides an efficient one-pot approach to parallel synthesis of secondary amines by the reductive amination of ketones. The approach demonstrated its applicability to a variety of substrates with different degree of hindrance of an amino or a carbonyl group affording products in moderate to high yields.

One-pot parallel synthesis of unsymmetrical aliphatic ureas was achieved with bis(2,2,2-trifluoroethyl) carbonate. The procedure worked well for both the monosubstituted and functionalized alkyl amines and required no special conditions (temperature control, order, or rate of addition). A library of 96 diverse ureas was easily synthesized.

Two types of aliphatic sulfonyl halides (Cl versus F) were compared in parallel synthesis of sulfonamides derived from aliphatic amines. Aliphatic sulfonyl fluorides showed good results with amines bearing an additional functionality, while the corresponding chlorides failed. Both sulfonyl halides were effective in the reactions with amines having an easily accessible amino group. Aliphatic sulfonyl chlorides reacted efficiently with amines bearing sterically hindered amino group while the corresponding fluorides showed low activity.

A parallel reductive amination of heteroaromatic amines has been performed using a combination of ZnCl2-TMSOAc (activating agents) and NaBH(OAc)3 (reducing agent). A library of diverse secondary amines was easily prepared on a 50-300 mg scale.

An efficient solution-phase parallel synthesis of alkylated guanidines from commercial thioisocyanates and amines is described. In the first step, a thioisocyanate reacts with one equivalent of ammonia or a primary or secondary amine to give a thiourea intermediate. The latter is S-alkylated with n-dodecyl bromide resulting in the corresponding thiouronium bromide. Finally, the reaction of the thiouronium salt with a second equivalent of ammonia or a primary amine yields an alkylated guanidine. All three synthetic steps are easily combined in a one-pot high-yielding procedure with a simple work-up. Ca. 250 guanidine derivatives with high structural and functional diversity were synthesized by the developed method. 35 representatives reported in this study were fully characterized.

The synthesis of a new d-glucosamine-based dicyclohexylarylphosphine has been developed. The catalytic performance of this neutral ligand is demonstrated in the Suzuki–Miyaura cross-coupling reaction between several arylboronic acids and aryl or heteroaryl chlorides.

The synthesis of a new generation of chiral phosphine-amides derived from d-glucosamine is described. The palladium-catalyzed asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate with dimethyl malonate has been investigated. The results obtained from these new ligands showed the importance of the rigidity of the complex and of the d-glucosamine skeleton on the enantioselectivity of the reaction.