The Cycloaddition Reaction of Lawesson's Reagent with 1,3-Dienes

Lawesson's reagent undergoes [2 + 4] cycloaddition reaction with 2-methyl-1, 3-butadiene,cyclopentadiene to yield heterocycles 4 and 5, respectively.

A Convenient and Efficient Route to 1,4-Bis（heteroaryl）-buta-1,3-diene and 4-Heteroarylbut-1-en-3-yne from 1,4-Dichlorobut-2-yne

A convenient and practical route to functionalized conjugated 1,3-enynes and 1,3-dienes is described. 1,4-Bis（heteroaryl）- 1,3-diene and 1-heteroarylbut- 1-en-3-yne derivatives were prepared from 1,4-dichloro-2-butyne and corresponding N-heteroarenes such as imidazole, pyrrole, pyrazole and indole derivatives in the presence of bases in good to high yields.

Stereoselective Synthesis of Functionalized 1,3-Dienes in Water

An efficient synthesis of functionalized 1,3-dienes via one-pot reactions between dialkyl acetylenedicarboxylates, 1,3-dicarbonyl compounds and secondary amines in water as the solvent is described. The mild reaction condition high yields and the new products are advantages of our method.

Palladium-Catalyzed Formal [4＋2] Cycloaddition of Benzoic and Acrylic Acids with 1,3-Dienes via C-H Bond Activation： Efficient Access to 3,4-Dihydroisocoumarin and 5,6-Dihydrocoumalins

We report a palladium-catalyzed formal intermolecular [4＋2] cycloaddition of benzoic and acrylic acids with 1,3-dienes including the stock chemicals 1,3-butadiene and isoprene leading to synthetically useful 3,4-dihydroisocoumarins and 5,6-dihydrocoumalins. Stepwise C-H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.

Palladium-Catalyzed Cascade Double C--N Bond Activation： A New Strategy for Aminomethylation of 1,3-Dienes with Aminals

A new palladium-catalyzed selective aminomethylation of conjugated 1,3-dienes with aminais via double C-N bond activation is described. This simple method provides an effective and rapid approach for the synthesis of linear a,13-unsaturated allylic amines with perfect regioselectivity. Mechanistic studies disclosed that one palladium catalyst cleaved two distinct C-N bond to furnish a cascade double C-N bond activation, in which an allylic 1,3-diamine and allylic 1,2-diamine were initially formed as key intermediates through the palladium-catalyzed C-N bond activation of aminal and the α,β-unsaturated allylic amine was subsequently produced via palladium-catalyzed C-N bond activation of the allylic diamines.

Highly Stereoselective Synthesis of Phenylseleno-and p-Tolylsulfonyl Substituted 1,3-Dienes from Functionalized Allyl Alcohols

Phenylseleno- and p-tolylsulfonyl substituted 1,3-dienes were conveniently prepared with high stereoselectivity by the elimination reaction of phenylseleno- and p-tolylsulfonyl substituted allyl alcohols in the presence of BF3·Et2O in acetic anhydride. The products were characterized by 1H NMR, MS, IR and elemental analysis. The single crystal structure of 2a was determined by X-ray diffraction analysis.

Design,synthesis,and applications of stereospecific 1,3-diene carbonyls

The strategy toward the synthesis of various 1,3-dienals or 1,3-dienones is disclosed between diazo compounds and furans,which features metal-free,additive-free,broad functional group tolerance,and readily accessible starting materials.Notably,this strategy is applicable in both intramolecular and intermolecular protocols.Mechanistic studies suggested that the reactions undergo a cyclopropanation/rearrangement sequence.With an E/E-1,3-dienal,corresponding N-tosylhydrazones were readily prepared and subjected to phenylboronic acid to form a double bond migration product and indoles to construct a five-member ring via [3 + 2] annulation reaction.

Photoinduced and palladium-catalyzed hydrogen atom transfer triggered 1,2-difunctionalization of 1,3-dienes with hydroxamides

The discovery of novel catalysis modes to generate a significant increase in structural complexity from readily available reactants is a fundamental goal in modern organic synthesis.Here,we report a photoinduced palladium-catalyzed hydrogen atom transfer triggered 1,2-difunctionalization of conjugated dienes.Without the employment of exogeneous photosensitizers and external oxidants,the cascade reaction realized the integration of remote functionalization of various C(sp^(3))-H bonds and selective difunctionalization of 1,3-dienes with 100% atom efficiency,allowing for the synthesis of structurally diverse amides with up to 90% yields.Given the prevalence of amides in pharmaceuticals and natural products,the current protocol has provided an efficient means to access highly functionalized amides from readily available carboxylic acid derivatives and 1,3-dienes.

Pd-catalyzed halocyclizations of unactivated 1,6-diynes through a formal anti-carbopalladation/bromide radical cascade

We report a Pd-catalyzed halocyclization of unactivated 1,6-diynes with N-bromosuccinimide(NBS).This approach produces stereo-defined dibromo substituted dihydropyrans,tetrahydropyridines,and 3-methylene cyclohexenes with exocyclic double bond appendages in mostly good yields.Copper salt was found to be a useful Lewis acid in this reaction.Mechanistically,a formal anti-carbopalladation and a bromide radical promoted PdⅡ-PdⅢ-PdⅠ-PdⅡcatalytic cycles were proposed to be involved in the formation of the dibromo-substituted products.Further functionalization of the dihydropyran derivatives underwent B(C6F5)3-catalyzed ring opening,and reduction afforded dibrominated 1,3-dienes with excellent stereoselectivity.

Simple nucleophile/H_(2)O promoted defluorinative ring-opening of gem-difluorocyclopropenes

A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented,providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio-and stereoselectivities.The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents.Water plays a crucial role in this transformation.

Enantioselective and stereodivergent hydromonofluoroalkylation of conjugated and remote diene

Because of the widespread applications of optically active alkyl fluorides in medicinal and agro chem-icals,enantioselective and even stereodivergent construction of alkyl fluorides remains highly desirable but underdeveloped.Transition-metal-catalyzed asymmetric hydrofluoroalkylation of readily available di-enes represents a novel route to achieve this goal,yet receives scarce study.Here we report an intrigu-ing palladium-catalyzed enantioselective hydromonofluoroalkylation reaction of conjugated dienes.Both monosubstituted and internal dienes proceed well with the transformation and furnish alkyl fluorides in generally>80%yield and>90%ee.A stereodivergent hydromonofluoroalkylation protocol via Pd/Cu co-catalysis is also established for the access to all four stereoisomers of corresponding moieties bear-ing a fully-substituted F-stereogenic center and vicinal tertiary carbon center.In addition,asymmetric migratory hydromonofluoroalkylation of skipped dienes is developed to realize the direct allylic C-H flu-oroalkylation.A compound library of enantioenriched cyclic fluorides is thus built to highlight the trans-formation potential of present methodology.