Na2CO3-promoted synthesis of thiocarbamates from isocyanates and thiols under mild conditions

Here, we developed an efficient method for the synthesis of s-alkyl or aryl thiocarbamates catalyzed by Na2CO3 under mild conditions using alkyl or aryl isocyanates and thiophenols or thiols. In situ reaction with deuterated tetrahydrofuran (d8-THF) was carried out to investigate the reaction mechanism. This method has the advantages of high yield, good functional group tolerance and high atom economy.

Direct synthesis of carbamates, thiocarbamates, and ureas from Boc-protected amines: a sustainable and efficient approach

In the quest for sustainable and efficient synthetic methodologies within medicinal chemistry, the synthesis of carbamates and their derivatives holds a pivotal role due to their widespread application in bioactive compounds. This investigation unveils a novel methodology for the straightforward transformation of Boc-protected amines into carbamates, thiocarbamates, and ureas, utilizing tert-butoxide lithium as the sole base. This approach effectively obviates the necessity for hazardous reagents and metal catalysts, presenting marked enhancements compared to traditional synthetic pathways. Notably, the method demonstrates facile scalability to gram-level production. This study contributes to the advancement of sustainable synthetic methodologies, offering a more benign and efficient alternative for the synthesis of key chemical intermediates with implications for broad pharmaceutical and agrochemical applications.

Direct C-H Sulfuration: Synthesis of Disulfides, Dithiocarbamates, Xanthates, Thiocarbamates and Thiocarbonates

In light of the important biological activities and widespread applications of organic disulfides, dithiocarbamates, xanthates, thiocarbamates and thiocarbonates, the continual persuit of efficient methods for their synthesis remains crucial. Traditionally, the preparation of such compounds heavily relied on intricate multi-step syntheses and the use of highly prefunctionalized starting materials. Over the past two decades, the direct sulfuration of C-H bonds has evolved into a straightforward, atom- and step-economical method for the preparation of organosulfur compounds. This review aims to provide an up-to-date discussion on direct C-H disulfuration, dithiocarbamation, xanthylation, thiocarbamation and thiocarbonation, with a special focus on describing scopes and mechanistic aspects. Moreover, the synthetic limitations and applications of some of these methodologies, along with the key unsolved challenges to be addressed in the future are also discussed. The majority of examples covered in this review are accomplished via metal-free, photochemical or electrochemical approaches, which are in alignment with the overraching objectives of green and sustainable chemistry. This comprehensive review aims to consolidate recent advancements, providing valuable insights into the dynamic landscape of efficient and sustainable synthetic strategies for these crucial classes of organosulfur compounds.

Chemo- and Site-Selective Replacement of N-Terminal Carbamates in Peptides

In peptide synthesis, it is important to distinguish the terminal amino group and carry out the selective transformation of only the N-terminal protecting group. We describe herein a reaction for the chemo- and site-selective replacement of carbamates with various other carbamates only at the N-terminus of peptides. We demonstrate the scope of carbamates and peptides and the introduction of fluorine into a peptide. This strategy is applicable to the late stage of peptide synthesis.

New efficient synthesis of tRNA related adenosines bearing the hydantoin ring (ct6A, ms2ct6A) by intramolecular cyclization of N6-(N-Boc-α-aminoacyl)-adenosine derivatives

A novel and efficient way for synthesis of N6-hydantoin modified adenosines, which utilizes readily available N6-(N-Boc-α-aminoacyl)-adenosine derivatives, was developed. The procedure is based on the epimerization free Tf2O-mediated conversion of the Boc group into an isocyanate moiety, followed by intramolecular cyclization. Using this method two recently discovered hydantoin modified tRNA adenosines, i.e. cyclic N6-threonylcarbamoyl-adenosine (ct6A) and 2-methylthio-N6-threonylcarbamoyladenosine (ms2ct6A) were prepared in good yields.

N-Substituted S-Alkyl Carbamothioates in the Synthesis of Nitrogen-containing Functional Derivatives of the Adamantane Series

A series of new asymmetric ureas, urethanes, and other derivatives of the framework structure have been synthesized by the reactions of adamantan-1-yl isocyanate generated in situ by the thermolysis of carbamothioates with nitrogen-containing nucleophiles and alcohols.

Practical one-pot amidation of N-Alloc-, N-Boc-, and N-Cbz protected amines under mild conditions

A facile one-pot synthesis of amides from N-Alloc-, N-Boc-, and N-Cbz-protected amines has been described. The reactions involve the use of isocyanate intermediates, which are generated in situ in the presence of 2-chloropyridine and trifluoromethanesulfonyl anhydride, to react with Grignard reagents to produce the corresponding amides. Using this reaction protocol, a variety of N-Alloc-, N-Boc-, and N-Cbz-protected aliphatic amines and aryl amines were efficiently converted to amides with high yields. This method is highly effective for the synthesis of amides and offers a promising approach for facile amidation.

One-pot efficient transformation of N-Alloc-, N-Boc-, and N-Cbz protected amines to amides was achieved by using 2-chloropyridine and trifluoromethanesulfonyl anhydride as well as Grignard reagent and MgCl₂.

N-Acylbenzotriazoles as Proficient Substrates for an Easy Access to Ureas, Acylureas, Carbamates, and Thiocarbamates via Curtius Rearrangement Using Diphenylphosphoryl Azide (DPPA) as Azide Donor

A diverse range of ureas, N-acylureas, carbamates, and thiocarbamates has been synthesized in good to excellent yields by reacting N-acylbenzotriazoles individually with amines or amides or phenols or thiols in the presence of diphenylphosphoryl azide (DPPA) as a suitable azide donor in anhydrous toluene at 110 °C for 3–4 hours. In this route, DPPA was found to be a good alternative to trimethylsilyl azide and sodium azide for the azide donor in Curtius degradation. The high reaction yields, one-pot and metal-free conditions, straightforward nature, easy handling, use of readily available reagents, and in many cases avoidance of column chromatography are the notable features of the devised protocol.

Simple and efficient synthesis of bicyclic enol-carbamates: access to brabantamides and their analogues

A simple and short synthesis of bicyclic enol-carbamates with high E/Z selectivity and the synthesis of brabantamide A analogue are presented.

Urea Derivatives in Modern Drug Discovery and Medicinal Chemistry

The urea functionality is inherent to numerous bioactive compounds, including a variety of clinically approved therapies. Urea containing compounds are increasingly used in medicinal chemistry and drug design in order to establish key drug-target interactions and fine-tune crucial drug-like properties. In this perspective, we highlight physicochemical and conformational properties of urea derivatives. We provide outlines of traditional reagents and chemical procedures for the preparation of ureas. Also, we discuss newly developed methodologies mainly aimed at overcoming safety issues associated with traditional synthesis. Finally, we provide a broad overview of urea-based medicinally relevant compounds, ranging from approved drugs to recent medicinal chemistry developments.

Structural and chemical insights into the covalent-allosteric inhibition of the protein kinase Akt

The Ser/Thr kinase Akt (Protein Kinase B/PKB) is a master switch in cellular signal transduction pathways. Its downstream signaling influences cell proliferation, cell growth, and apoptosis, rendering Akt a prominent drug target. The unique activation mechanism of Akt involves a change of the relative orientation of its N-terminal pleckstrin homology (PH) and the kinase domain and makes this kinase suitable for highly specific allosteric modulation. Here we present a unique set of crystal structures of covalent-allosteric interdomain inhibitors in complex with full-length Akt and report the structure-based design, synthesis, biological and pharmacological evaluation of a focused library of these innovative inhibitors.

Metal-Free Catalytic Synthesis of Thiocarbamates Using Sodium Sulfinates as the Sulfur Source

A novel molecular iodine-catalyzed protocol for the construction of thiocarbamates from readily available sodium sulfinates, isocyanides, and water has been described. The present methodology offers a facile and practical route to a variety of thiocarbamates in moderate to good yields with favorable functional group tolerance by use odorless sodium sulfinates as the sulfur source. The mechanistic studies suggest the present transformation involves a radical process.

Direct thiocarbamation of imidazoheterocycles via dual C–H sulfurization

Direct thiocarbamation via dual C–H sulfurization.

Molecular iodine-mediated synthesis of thiocarbamates from thiols, isocyanides and water under metal-free conditions

A simple and practical molecular iodine-mediated method for the efficient construction of thiocarbamates from isocyanides, thiols and water under metal-free and mild conditions has been developed. A variety of thiocarbamates were easily synthesized through this methodology, which has the advantages of simple operation, eco-friendly conditions, good functional group tolerance, and readily accessible raw materials.

Spontaneous and Direct Transformation of N,O-Diaryl Carbamates into N,N'-Diarylureas

We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N'-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (Et₃N) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates. Substrates bearing an electron-donating methoxy group on either of the aryl groups reacted slowly under these conditions.

Palladium-catalyzed C(carbonyl)–C bond cleavage of amides: a facile access to phenylcarbamate derivatives with alcohols

A sulfur-containing auxiliary enabled palladium-catalyzed C(carbonyl)–C bond activation of amides was reported to form phenylcarbamate derivatives with alcohols.

Iodine-catalyzed cross-coupling of isocyanides and thiols for the synthesis of S-thiocarbamates

Synthesis of S-thiocarbamates by employing simple and readily available precursors under mild reaction conditions with good to excellent yields.

Ureas as safe carbonyl sources for the synthesis of carbamates with deep eutectic solvents (DESs) as efficient and recyclable solvent/catalyst systems

A simple, efficient and eco-friendly one-pot synthesis of primary, N-mono- and N-disubstituted carbamates is developed from ureas.

Metal-free direct thiocarbamation of imidazopyridines with carbamoyl chloride and elemental sulfur

Metal-free direct thiocarbamation of imidazopyridines using elemental sulfur.