Palladium-catalyzed carbonylative synthesis of N-cyanobenzamides from aryl iodides/bromides and cyanamide

A novel and convenient protocol for the synthesis of N-cyanobenzamides starting from readily available aryl halides and cyanamide via palladium-catalyzed aminocarbonylation has been developed. The protocol utilizes Mo(CO)₆ as the CO source or CO(gas) and affords the desired N-cyanobenzamides in moderate to good yields.     

Chemo- and diastereoselective cyclopropanation of allylic amines and carbamates

A highly chemo- and diastereoselective protocol for the cyclopropanation of tertiary allylic amines with Shi’s carbenoid [CF₃CO₂ZnCH₂I] is described. The high levels of diastereoselectivity observed in these reactions may be attributed to chelation of the nitrogen atom to the zinc reagent, which then transfers a methylene unit to the syn-face of the olefin. Furthermore, a stereodivergent protocol for the cyclopropanation of a range of allylic carbamates has been developed, which provides access to both diastereoisomers of the corresponding cyclopropanes with very high levels of diastereoselectivity: cyclopropanation with the Wittig-Furukawa reagent [Zn(CH₂I)₂] proceeds under chelation control to give the corresponding syn-product, whilst reaction with Shi’s carbenoid proceeds under steric control to give the corresponding anti-cyclopropane, in >95:5 dr in both cases.     

A convenient one-pot synthesis of 3,5-diarylisoxazoles via oxidative cyclisation using catalytic CuBr2 and oxone

A facile one-pot synthesis of 3,5-diarylisoxazoles from α,β-unsaturated ketones and hydroxylamine hydrochloride is reported. The reaction is efficiently promoted by catalytic CuBr₂ and Oxone to afford the desired products mostly in high yields and in relatively short time. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol. This protocol is effective toward various substrates having different functionalities.     

Nickel-catalyzed regio- and stereoselective hydrophosphinylation of internal ynamides with H-phosphinates

A method for the catalytic hydrophosphinylation of internal ynamides with H-phosphinates has been developed for the first time. The protocol employing the catalyst generated from NiBr₂ and PPh₃ could be applied to several types of ynamides and H-phosphinates, affording (E)-β-aminovinylphosphinates in a highly regio- and stereoselective manner.     

CeCl3-mediated addition of acetylenic bis-lithium salts to aldehydes and ketones: An efficient route to bis-substituted alkyne diols

An efficient, chemoselective protocol to access propargylic diols via a CeCl₃-mediated addition reaction is reported. Propargylic alcohols were transformed into the corresponding acetylenic bis-lithium salt intermediates, which react with aldehydes and ketones in the presence of dry CeCl₃ to furnish the corresponding bis-substituted alkyne diols. This protocol does not involve protection-deprotection or transmetallation steps, and allows the use of poorly reactive or highly enolizable substrates.     

Asymmetric C–H insertion of Rh(II) stabilized carbenoids into acetals: A C–H activation protocol as a Claisen condensation equivalent

The dirhodium tetraprolinate, Rh₂(S-DOSP)₄ is an efficient catalyst in an enantioselective C–H activation protocol. Rh₂(S-DOSP)₄ catalyzed decomposition of aryldiazoacetates or vinyldiazoacetates results in the formation of transient rhodium carbenoid intermediates. These intermediates are capable of selectively inserting into the C–H bond of acetals. The resulting products are protected β-keto esters, and so the C–H activation protocol can be considered as strategically equivalent to the Claisen condensation.     

Regioselective synthesis of calix[4]arene 1,3-di- and monosubstituted sulfur-containing Schiff bases

Regioselective alkylations of p-tert-butylcalix[4]arene with 3-methoxy-4-ω-chloroalkoxy-benzaldehydes in the system of K₂CO₃/KI/CH₃CN efficiently produce 1,3-di- and monosubstituted aldehydes according to the length of alkyl chains in alkylating reagent, which provides a versatile protocol for preparing calixarene 1,3-di- and sulfur-containing Schiff bases.     

Application of cyclic-1,3-diketones in domino and multicomponent reactions: facile route to highly functionalized chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones under solvent-free conditions

A facile and efficient protocol for the synthesis of chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones has been developed by one-pot three-component cyclocondensation of aldehydes, cyclic-1,3-diketones and 1,3-dimethylbarbituric acid in the presence of InCl₃ or P₂O₅ under solvent-free conditions.     

Tandem enantioselective conjugate addition-Mannich reactions: efficient multicomponent assembly of dialkylzincs, cyclic enones and chiral N-sulfinimines

A convenient access to enantiopure β-amino ketones through a multicomponent reaction of dialkyl zinc reagents, cyclic enones and chiral N-tert-butanesulfinimines is disclosed. Four diastereoisomers can be selectively obtained by the appropriate choice of the chiral ligand (L or ent-L) and the chiral N-sulfinimine (R_S or S_S). The protocol is particularly efficient when enolisable N-sulfinimines are used.     

NH4I/EtOCS2K promoted synthesis of substituted benzils from diphenylacetylene derivatives

A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH₄I/EtOCS₂K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH₄I promoted EtOCS₂K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.     

Regioselective dehydroxytrifluoromethylthiolation of allylic and propargylic alcohols with AgSCF3

The reaction of easily available Morita–Baylis–Hillman (MBH) alcohols with AgSCF₃ in the presence of n-Bu₄NI and KI affords primary allylic SCF₃ products in high yields and excellent regioselectivities. This regioselective dehydroxytrifluoromethylthiolation protocol could also be extended to propargylic alcohols for the preparation of the primary propargylic SCF₃ products.     

Synthesis and characterization of polybrominated fluorenes and their conversion to polyphenylated fluorenes and cyclopenta[def]triphenylene

We report the synthesis and characterization of polyphenylated fluorene derivatives and a ring cyclized product containing cyclopenta[def]triphenylene core. Polybromination on fluorene was achieved either by solid state reaction with bromine or utilizing Br₂/KBrO₃ in AcOH/H₂SO₄ mixture. The bromofluorenes were converted to the corresponding polyphenylated fluorenes by Suzuki coupling protocol. A hexabromofluorene underwent a multifold Suzuki coupling followed by C–H activation to produce a cyclopenta[def]triphenylene derivative. Fluorene ring showed a severe distortion from planarity beyond tetra-substitution which manifested in the optical properties.     

Regio- and stereoselective hydroxybromination and dibromination of olefins using ammonium bromide and oxone®

An efficient protocol for the synthesis of vicinal bromohydrins and dibromides from olefins is presented. Various olefins are regio- and stereoselectively hydroxybrominated and dibrominated with anti fashion, following Markonikov’s rule, using eco-friendly, non-toxic, and stable reagents such as NH₄Br and oxone® in CH₃CN/H₂O (1:1) and CH₃CN without employing catalyst in moderate to excellent yields. Bromohydrins are formed instantaneously.     

A chemoenzymatic-RCM strategy for the enantioselective synthesis of new dihydroxylated 5-hydroxymethyl-indolizidines and 6-hydroxymethyl-quinolizidines

A direct method for the synthesis of new azasugars-like compounds has been developed, which involves a new biocatalytic protocol based on the use of a lipase from Candida Cylindracea and of a ionic liquid as reaction medium, to prepare the key C₁-symmetric piperidine precursor. By subsequent application of RCM reactions and OsO₄-catalyzed double bond syn-dihydroxylation, the synthesis of the target compounds could be accomplished in a straightforward and stereocontrolled manner.     

Iron-catalyzed aerobic oxidative cross-coupling amidation of N,N-dimethylanilines

An efficient iron-catalyzed dehydrogenative cross-coupling amidation/imidation reaction between N,N-dimethylanilines and amides/imides is reported. The protocol uses an inexpensive and readily available Fe(NO₃)₃·9H₂O/O₂ catalytic system in the absence of additional ligands at room temperature.     

Transition-metal-free trifluoromethylthiolation and difluoromethylthiolation of thiols with trifluoromethanesulfonyl chloride and difluoromethanesulfonyl chloride

Triphenylphosphine-mediated metal-free trifluoromethylthiolation and difluoromethylthiolation of thiols by CF₃SO₂Cl and CHF₂SO₂Cl to synthesize trifluoromethyl disulfides and difluoromethyl disulfides, respectively, was achieved at room temperature. Iodine generated in situ from iodide facilitated this reaction via the formation of iodotriphenylphosphonium iodide which could serve as a reducing agent in this transformation. Readily available reagents and mild reaction conditions without transition-metals allow this protocol to be more practical than traditional methods.     

NH4I-promoted N-acylation of amines via the transamidation of DMF and DMA under metal-free conditions

An unprecedented NH₄I-promoted N-formylation and N-acetylization of various amines with dimethylformamide (DMF) and dimethylacetamide (DMA) has been developed. This protocol shows broad substrate scope for aromatic, aliphatic, and heterocyclic amines, which provides a metal-free strategy for N-acylation featuring mild reaction conditions, as well as inexpensive and readily available starting materials.     

A novel approach for the one-pot synthesis of linear and angular fused quinazolinones

A convenient and inexpensive one step methodology has been developed for the synthesis of linear and angular fused quinazolinones. The protocol, which uses amino heterocycles and o-bromo benzyl/naphthyl bromides as reactants, CuI as catalyst, Cs₂CO₃ as base, l-proline as ligand, and DMF as solvent, proceeds via nucleophilic aromatic substitution of the N-heteroaromatic cationic intermediate followed by in situ aerial oxidation at the benzylic position to the quinazolinone scaffold.     

A new application for diethyl azodicarboxylate: efficient and regioselective thiocyanation of aromatics amines

Highly regioselective thiocyanations of indoles, anilines and pyrrole are achieved via an efficient and simple protocol using NH₄SCN and diethyl azodicarboxylate (DEAD) as a mild oxidant.     

A general method for regioselective Heck arylation of electron-rich N-acyl-N-vinylamine with aryl halides

A highly efficient protocol for the Pd-catalyzed regioselective Heck arylation of the electron-rich olefin N-acyl-N-vinylamine with aryl halides has been developed. In the presence of hydrogen-bond donor [H₂NiPr₂][BF₄] as an additive, this proceeds smoothly in isopropanol to afford exclusively the branched products in high yields.