An efficient stereoselective synthesis of (+)-deoxoprosophylline

An efficient stereoselective synthesis of (+)-deoxoprosophylline from readily available p-anisaldehyde is described. Key steps in the synthesis include the stereoselective amination of anti-1,2-dibenzyl ether using chlorosulfonyl isocyanate, intermolecular olefination, and Pd-catalyzed intramolecular cyclization.     

Tartaric acid-derived chiral phosphite-type P,N-ligands: behavioural features in Pd-catalyzed asymmetric transformations

A practical synthesis of new phosphoramidite, phosphite and diamidophosphite P,N-ligands derived from (R,R)-tartaric acid was carried out. A study of these chiral inducers showed them to provide up to 93% ee in the Pd-catalyzed asymmetric allylations of (E)-1,3-diphenylallyl acetate, up to 84% ee in the Pd-catalyzed asymmetric alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate and up to 63% ee in the Pd-catalyzed desymmetrization of N,N′-ditosyl-meso-cyclopent-4-ene-1,3-diol biscarbamate. The effects of the structural modules, such as the nature of the phosphorus-containing ring or exocyclic substituent as well as of the nature of palladium source on the catalytic activity and enantioselectivity were investigated.     

Enantioselective total synthesis of (+)-vincamine

A catalytic asymmetric total synthesis of (+)-vincamine is presented. Key features of the synthesis include a Pd-catalyzed enantioselective decarboxylative allylation to form the C20 quaternary stereogenic center and a stereoselective iminium reduction to install the critical cis-C20/C21 relative stereochemisty.     

Synthesis of new polyaza heterocycles. Part 42: Diazines

Using Pd-catalyzed Stille cross-coupling reactions, we report here the synthesis of various mono- or bis(tri-n-butylstannyl)diazines which were reacted with various halogenated diazines to access to various polyaza heterocyclic derivatives.     

Stepwise and one-pot cross-coupling-heteroannulation approaches toward 2-substituted C5-, C6-, and C7-nitroindoles

A general and efficient synthesis of 2-substituted C5-, C6-, and C7-nitroindoles has been established. Starting from commercially available 2-amino nitrophenols, C5-, C6-, and C7-nitroindoles were synthesized via the stepwise Pd-catalyzed cross-coupling of nitro 2-trifloxyanilides with 1-alkynes followed by the t-BuOK-mediated heteroannulation. A Pd-catalyzed one-pot coupling-heteroannulation procedure was carried out by using nitro 2-trifluoroacetamidoaryl triflates.     

Stereoselective transformation of easily available (2Z,4E)-2,4-alkadien-1-ols into (E)-3-alkene-1,2,5-triol derivatives

Synthesis of 3-alkenyl-1,2,5-triol derivatives, potentially useful intermediates in organic synthesis, is established, which constitutes stereoselective epoxidation of the hitherto hardly accessible dienyl alcohols of the cis,trans stereochemistry followed by Pd-catalyzed reaction with AcOH.     

Stereoselective synthesis of imidazolidin-2-ones via Pd-catalyzed alkene carboamination. Scope and limitations

A method for the synthesis of imidazolidin-2-ones from N-allylureas and aryl or alkenyl bromides via Pd-catalyzed carboamination reactions is described. The N-allylurea precursors are prepared in one step from readily available allylic amines and isocyanates, and the Pd-catalyzed reactions effect the formation of a C-C bond, a C-N bond, and up to two stereocenters in a single step. Good diastereoselectivities are obtained for the conversion of substrates bearing allylic substituents to 4,5-disubstituted imidazolidin-2-ones, and excellent selectivity for the generation of products resulting from syn-addition across the alkene is observed when substrates derived from cyclic alkenes or E-1,2-disubstituted alkenes are employed. A brief discussion of reaction mechanism and product stereochemistry is presented.     

Synthesis of chiral unsaturated aminolactones using Pd-catalyzed allylic amination

Stereoselective synthesis of (5R,6R)- and (5S,6S)-5-benzylamino-6-(tert-butyldimethylsilanyloxymethyl)-5,6-dihydropyran-2-ones starting from d-glucal and furanaldehyde, respectively, is described. The synthesis relies on a Sharpless asymmetric dihydroxylation, an Achmatowicz reaction, and a stereoselective Pd-catalyzed allylic amination as the key steps.     

Pd-catalyzed asymmetric allylic alkylation with nitromethane using a chiral diaminophosphine oxide: (S,RP)-Ph-DIAPHOX. Enantioselective synthesis of (R)-preclamol and (R)-baclofen

A Pd-catalyzed asymmetric allylic alkylation with nitromethane using an aspartic acid-derived P-chirogenic diaminophosphine oxide [(S,R_P)-Ph-DIAPHOX] is described. This method was successfully applied to enantioselective synthesis of (R)-preclamol and (R)-baclofen.     

Synthesis of E-vinyl iodides via Pd-catalyzed hydrostannation of terminal alkynes

E-Vinyl iodides may be prepared via a one-pot reaction involving Pd-catalyzed hydrostannation of terminal alkynes followed by iodinolysis of the intermediate vinylstannane. The synthesis is tolerant of functional groups, such as alcohols and esters.     

Practical synthesis and applications of benzoboroxoles

A convenient one-pot synthesis of benzoboroxoles has been developed via the reaction of o-bromobenzyl alcohols with NaH, ⁿBuLi, and B(OⁱPr)₃ followed by acidic hydrolysis. Applications of these benzoboroxoles have been demonstrated in Pd-catalyzed cross-coupling reactions and the protocol has been extended for the synthesis of a chiral benzoboroxole. Exceptionally short synthesis of a potent antifungal agent AN2690 and several of its analogs has also been realized.     

Pd-Catalyzed asymmetric transformations involving P*-mono- and P*,N-bidentate diamidophosphites derived from (2S,3S)-N 2,3-dimethyl-N 1-phenylpentane-1,2-diamine

The synthesis of new P*-mono- and P*,N-bidentate diamidophosphites, containing 1,3,2-diazaphospholidine rings formed starting from (2S,3S)-N ²,3-dimethyl-N ¹-phenylpentane-1,2-diamine, is described. Comparison of their efficiency in the Pd-catalyzed enantioselective allylation with (E)-1,3-diphenylallyl acetate showed that up to 97% ee was reached in the reaction involving dimethyl malonate as a C-nucleophile. The Pd-catalyzed desymmetrization of N,N′-ditosyl-meso-cyclopent-4-ene-1,3-diol biscarbamate gave up to 61% ee.     

Synthesis of dihydroindenofuran scaffold via a Pd-catalyzed 5-endo-trig cyclization/enolate O-alkylation cascade

An efficient synthesis of dihydroindenofurans was carried out starting from the Baylis-Hillman adducts via a Pd-catalyzed 5-endo-trig-carbopalladation and enolate O-alkylation cascade as a key step. This is the first example of enolate O-alkylation with a C(sp³)-bound palladium intermediate.     

Pd-catalyzed cross-coupling/heterocyclization domino reaction: facile access to anthra[2,3-b]furan-5,10-dione scaffold

A new facile route to the synthesis of 4,11-dimethoxyanthra[2,3-b]furan-5,10-dione and its novel 2-substituted derivatives was proposed. The developed scheme was based on a Pd-catalyzed cross-coupling/heterocyclization domino reaction of 3-bromo-2-hydroxy-4,11-dimethoxyanthraquinone with terminal alkynes.     

Concise and stereoselective synthesis of 2,5- and 2,4-disubstituted thiazole amino acid subunits for synthesizing thiazole-containing peptides

A concise, highly stereoselective synthesis of 2,4- and 2,5-disubstituted thiazole amino acids was developed. These are important building blocks for various biologically active thiazole-containing natural peptides and their regioisomeric analogues. The fundamental reactions are diastereoselective addition of (4- or 5-bromothiazol-2-yl)lithium to N-tert-butanesulfinyl imine with subsequent Pd-catalyzed phenoxycarbonylation.     

A novel multicomponent reaction to synthesize substituted furo[3,2-c]chromenes via a Pd-catalyzed cascade process

A novel one-pot three-component reaction for the synthesis of multisubstituted furo[3,2-c]chromenes using 3-(1-alkynyl)chromones, aryl iodides, and alcohols is developed via Pd-catalyzed cascade 1,4-addition and cyclization. This synthetic approach efficiently generates two C-O bonds and one C-C bond to construct diverse furo[3,2-c]chromenes structures.     

An efficient palladium-catalyzed synthesis of 1-heteroaryl-4-aminopiperidine derivatives from heteroaryl chlorides

An efficient protocol for the synthesis of 1-heteroaryl-4-(N-methyl)aminopiperidines starting from heteroaryl chloride derivatives is described. A broad range of 1-heteroaryl-4-(N-Boc-N-methyl)aminopiperidine derivatives were obtained in good to excellent yields using DavePhos as optimal ligand for Pd-catalyzed Buchwald-Hartwig amination reaction. After a mild and efficient acidolysis the amination products could be obtained successfully.     

Microwave-assisted multi-step synthesis of novel pyrrolo-[3,2-c]quinoline derivatives

A new approach for the synthesis of original substituted pyrrolo-[3,2-c]quinoline derivatives using microwave-assisted chemistry is described. The use of microwave activation in this synthesis resulted in high yielding and clean steps. The key step for introducing diversity is the amination or the Pd-catalyzed cross-coupling of an imidoyl chloride derivative, obtained in a straightforward manner and in good yield.     

Total synthesis of (−)-martinellic acid

An enantioselective formal total synthesis of the pyrrolo[3,2-c]quinoline natural product martinellic acid has been achieved. The key steps involve a Pd-catalyzed aryl amidation reaction of a pyrroglutamate derivative, an intramolecular [3+2] azomethine ylide-alkene cycloaddition and a reductive ring opening reaction.     

One-step construction of carbazoles by way of the palladium-catalyzed double N-arylation reaction and its application to the total synthesis of murrastifoline-A

The one-step construction of N-substituted carbazoles by way of the Pd-catalyzed double N-arylation reaction of primary amines with 2,2′-dibromobiphenyl is described. Aryl and aliphatic amines including tert-butylamine and a protected glucopyranosylamine were effectively transformed into the corresponding N-substituted carbazoles. The first total synthesis of murrastifoline-A, a biscarbazole alkaloid, based on this methodology is also presented.