查看更多>>摘要：Abstract Halogen (fluorine, chlorine, bromine, iodine) or chalcogen (sulfur, selenium)‐containing heterocycles are widely recognized as key building blocks in many natural products and bioactive targets. Catalytic asymmetric halogenation/chalcogenation of carbon‐carbon unsaturated bonds via onium ion transformations are efficient methods to obtain diverse chiral heterocyclic backbones. In the past few years, catalytic enantioselective versions of halo/thio/seleno‐functionalizations with various halogen and chalcogen electrophiles have experienced constant development. This review highlights those advances in preparing functionalized heterocycles promoted by chiral organocatalysts or metal‐based catalysts.
Max N. KliemannSimon TeeuwenChristopher WeikeGiancarlo Franciò...
7页
查看更多>>摘要：Abstract The catalytic asymmetric hydroformylation of styrenes was combined with condensation of the resulting aldehydes with acetohydrazide as nucleophile leading to γ‐chiral N’‐substituted aceto‐hydrazones. This cascade reaction is called hydrohydrazonemethylation (HHM) in analogy to similar hydroformylation/condensation sequences. The catalyst was formed in?situ from the commercially available chiral phosphine‐ligand (R,R)‐Ph‐BPE and [Rh(acac)(CO)2] and used at a loading of 0.2?mol%. The stable condensation products are not prone to tautomerization providing versatile chiral intermediates. Their one‐pot reduction with DMAB/TsOH resulted in the corresponding γ‐chiral N’‐substituted acetohydrazides (14 examples) with yields ranging from 73% to 91% and enantioselectivities from 77% to 97% ee. Deprotection of the acetohydrazides led to the corresponding β‐chiral hydrazines. Reduction and hydrogenolysis of the hydrazones over Raney‐Ni yielded the corresponding β‐chiral primary amines with 95% ee. Diastereoselective functionalization of the C=N bond of the hydrazones is a further synthetic option, as demonstrated by allylation with (allyl)SiCl3.
查看更多>>摘要：Abstract Photobiocatalysis fully utilizing the unique reactivity of photocatalysis and efficient transforming biobased feedstocks of biocatalysis represents a promising approach for future green synthesis. However, photobiocatalytic cascade with biobased starting substrates has been rarely reported. Here, we present photobiocatalytic cascades that modify the N‐heterocycle with keto acids biocatalytically synthesized from natural amino acids. The types of aliphatic, aromatic, and polar natural amino acids are compatible with the photobiocatalytic cascades system. In addition, the cascade is compatible with a range of N‐heterocycles with moderate to good yield (up to 82%). Furthermore, the cascade system can reach gram scale (0.91?g) with a good separation yield, demonstrating the potential for scaling up production to practical application. This photobiocatalytic cascade can synthesize a range of important N‐heterocyclic derivatives from natural amino acids in a green fashion and paves the way for greener synthesis by combining biocatalysis and photocatalysis.
查看更多>>摘要：Abstract A copper‐catalyzed multicomponent oxysulfonylation of alkenes with cyclobutanone oxime esters and hydroxamic acids via the insertion of sulfur dioxide has been developed. This reaction uses K2S2O5 as the sulfur dioxide surrogate and the in?situ generated amidoxyl radical as radical interceptor, thus providing a direct approach to β‐amidoxy sulfones in 35–90% yields. Mechanistic studies revealed that a radical‐radical coupling reaction of the alkyl radical and amidoxyl radical might be involved in this transformation.
查看更多>>摘要：Abstract We report a strategy for the preparation of 1,3‐dicarbonyl sulfoxonium ylides from α‐diazoketones and sulfoxonium ylides. The transformation is achieved based on the blue‐LEDs‐promoted Wolff rearrangement of the α‐diazoketones, and the nucleophilic nature of the sulfoxonium ylides. A large array of products was prepared to demonstrate the substrate scope and functional group tolerance. A plausible mechanism was proposed for this transformation based on the experimental results. Furthermore, the synthetic utility of the products was explored.
查看更多>>摘要：Abstract A direct (organo)catalytic method for the synthesis of chiral selenylated δ‐lactones via [4+2] annulation of selenyl vinyl ketones with enals has been achieved. The C5‐selenylated dihydropyranones were obtained in 54–88% yield with 90–99% enantioselectivity.
查看更多>>摘要：Abstract Herein, we disclosed an electrochemically induced method for the regio‐ and stereoselective (E)‐β‐C(sp2)?H trifluoromethylation of enamides by employing readily available and inexpensive Langlois’ reagent (CF3SO2Na). Preliminary mechanistic studies indicate the involvement of free radicals in the process. The exogenous oxidant‐free reaction proceeds in an undivided electrochemical cell under mild conditions and allows for the accomplishment of the trifluoromethylation products with exclusive E‐selective control. The methodology is featured by catalyst‐free, simple setup, and broad substrate scopes of enamides with good functional group tolerance. Using ArSO2Na as the coupling partner, the corresponding (E)‐β‐C(sp2)?H arylsulfonylated enamides products are obtained under standard reaction conditions.
Jyoti M. HonnanayakanavarPurna Chandra BeheraSurisetti Suresh
6页
查看更多>>摘要：Abstract A copper‐catalyzed tandem process integrating N‐arylation and 1,4‐conjugate addition is disclosed through the reaction of cyclic enaminones and ortho‐halochalcones. The reaction appears to proceed through chemoselective arylation on the nitrogen of enaminone with ortho‐halochalcones and Michael addition of α‐carbon of the enaminone to the chalcone to furnish a diverse range of tricyclic tetrahydroacridinone derivatives in moderate to excellent yields.
Alisa S. SunagatullinaFerdinand H. LutterKonstantin KaraghiosoffPaul Knochel...
5页
查看更多>>摘要：Abstract We report a new iron‐catalyzed I/Zn‐exchange allowing to convert primary or tailored secondary alkyl iodides into the corresponding alkylzinc iodides. In the presence of a remote double bond at position 5, diastereoselective ring closures are observed. Quenching of these zinc reagents, after transmetalation to copper species (with CuCN???2LiCl) or under Pd‐catalysis, with typical electrophiles (allyl bromides, acid chlorides or aryl iodides) gave various polyfunctional products.
NSTL
Wiley