Synthesis of poly-substituted pyrroles starting from the Baylis-Hillman adducts

We synthesized poly-substituted pyrrole derivatives 4a-e, 7a-c and 10a-d from the reaction of phenacyl bromide and the aza-Baylis-Hillman adducts 1a-d or their rearranged derivatives 5a-e. The pyrroles were synthesized via the successive N-alkylation, Michael addition, elimination of p-toluenesulfinic acid and oxidative aromatization processes.     

非传统介质中的Baylis-Hillman反应

Baylis-Hillman反应是一个为数不多的形成碳—碳键的原子经济反应, 因其产物富含官能团而成为非常有潜力的合成有机多功能分子的有力工具. 然而, 反应速度慢、反应产率低是该反应常遇到的问题. 为了克服这些缺点, 近年来, 许多新颖的溶剂被用于这个反应. 本文综述了这些方面的最新研究进展和发展趋势.     

Facile synthesis of γ-alkenylbutenolides from Baylis-Hillman adducts: consecutive in-mediated Barbier allylation, PCC oxidation, isomerization, and Zn-mediated Barbier allylation

Alkenylbutenolides were synthesized regioselectively in good to moderate yields from Baylis-Hillman adducts via a consecutive indium-mediated Barbier type reaction between Baylis-Hillman bromide and aldehyde, PCC oxidation of the homoallylic alcohol, double bond isomerization, and zinc-mediated Barbier type alkenylation protocol.     

Novel synthesis of naphtho[2,1-b]pyrano pyrrolizidines and indolizidines through intramolecular 1,3-dipolar cycloaddition reaction

A facile synthesis of a series of naphtho[2,1-b]pyrano pyrrolizidines and indolizidines was accomplished in good yields in a one-pot reaction through intramolecular 1,3-dipolar cycloaddition of azomethine ylides with Baylis-Hillman adducts as dipolarophiles. The protocol is applicable to a wide variety of photochromic and biologically active napthopyrano products. The regio and stereochemical outcome of the cycloaddition reaction was ascertained by X-ray crystallographic study of some of the products.     

Zinc mediated propenylation of Baylis-Hillman acetates

Allyl bromide efficiently reacts with Baylis-Hillman acetates in the presence of zinc and copper iodide resulting in substituted 1,5-dienes.     

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.     

Synthesis of five natural butanolides

Litseadioxanins A and B, the so far only known natural products with a dihydrodioxine ring at the terminal of a side chain, were synthesized for the first time. The peroxy functionality was installed via a photo [4 + 2] cycloaddition of O₂ to a multifunctional terminal 1,3-diene, a subtype of the reaction that has only a limited number of simple precedents (mostly monofunctional/with a much shorter alkyl chain) in the literature to date. LED was found to be superior to traditional mercury or tungsten lamps, not only giving better yields but also significantly simplifying the operations. The diene precursors (also natural products) to litseadioxanins were also synthesized for the first time. With the aid of the synthetic samples the previously unknown concentration/time–dependence of [α]_D of these dienes was revealed.     

Synthesis of 3,4-disubstituted 2,5-dihydrofurans starting from the Baylis-Hillman adducts via consecutive radical cyclization, halolactonization, and decarboxylation strategy

A facile synthetic method of 3,4-disubstituted 2,5-dihydrofurans and 2,5-dihydropyrroles starting from the Baylis-Hillman adducts was developed. The 2,5-dihydrofuran skeleton was constructed via the consecutive radical cyclization, hydrolysis, halolactonization, and spontaneous decarboxylation strategy starting from the modified Baylis-Hillman adducts.     

Base-catalyzed domino reaction toward 3-benzylidenecyclohexenes: DBU-promoted sequential Michael, aldol, dehydration, and dealkoxycarbonylation

3-Benzylidenecyclohexene derivatives were prepared starting from the Baylis-Hillman adducts by using DBU-promoted domino process involving Michael, aldol, dehydration, and dealkoxycarbonylation.     

Synthesis of substituted butenolides by the ring closing metathesis of two electron deficient olefins: a general route to the natural products of paraconic acids class

A variety of allyl acrylates possessing electron-withdrawing groups undergo RCM using the second generation Grubbs’ catalyst in the presence of a Lewis acid resulting in diverse butenolides in high isolated yields. This methodology provides a general route to the natural products of paraconic acids class, exemplified by a total synthesis of (±)-phaseolinic acid.