Macrocyclic propargyl acetates containing a furan ring were prepared by using a CrCl2‐promoted reaction. In the presence of either a AuI or AuIII catalyst, a tandem 3,3‐rearrangement/transannular [4+3] cycloaddition reaction occurred to give propargyl acetates that are regio‐ and diastereospecific. The regiochemistry of the product is controlled by the position of the acetoxy group in the starting material and the stereochemistry of the reaction depends on the ring size. 相似文献
An effective synthesis of structurally diverse benzazocines was accomplished in good to excellent chemical yields (55–82 %) through a gold(I)‐catalyzed cascade reaction involving tandem 1,2‐acyloxy shift/[3+2] cycloaddition of terminal 1,9‐enynyl esters. The reaction proceeds under extremely mild conditions and represents one of the relatively few transition‐metal‐catalyzed intramolecular cycloaddition reactions for the synthesis of benzazocines. 相似文献
A new synthetic route to the privileged 1,2‐dihydroisoquinolines is reported. This method, which relies on a gold‐catalyzed formal [4+2] cycloaddition between ynamides and imines, provides a new retrosynthetic disconnection of the 1,2‐dihydroisoquinoline core by installing the 1,8a C?C and 2,3 C?N bonds in one step. Both aldimines and ketimines can be used as substrates. In addition, one example of dihydrofuropyridine synthesis is also demonstrated. 相似文献
A gold‐catalyzed cycloisomerization of 1,6‐diynes containing an ynamide propargyl ester or carbonate moiety has been developed that provides an attractive route to a diverse‐substituted 3‐acyloxy‐1,4‐dihydrocyclopenta[b]indoles. Mechanistic studies indicate that the reaction likely proceeds through a competitive 1,2‐OAc migration followed by [3+2] cycloaddition of the vinyl gold–carbenoid intermediate with the pendant triple bond. The synthetic utility of the obtained cyclopenta[b]indole products was demonstrated by their efficient transformations by deprotection or double‐bond isomerization reactions. 相似文献
Ortho‐Alkynylbenzaldehydes have been widely used to generate isochromenylium derivatives through gold‐catalyzed cycloisomerization. These isochromenylium derivatives have been exploited as formal diene derivatives for reactions with different dienophiles. Herein, we describe the behavior of ortho‐alkynylsalicylaldehydes, a particular case of ortho‐alkynylbenzaldehydes. The gold‐catalyzed cycloisomerization of ortho‐alkynylsalicylaldehydes delivers an unusual heterodiene derivative that reacts with electron‐rich alkenes through a formal [4+2] cycloaddition. In this reaction, both the diene and dienophile are generated in situ through gold‐catalyzed cycloisomerization of appropriate alkynamines or alkynols. This reaction was used to synthesize complex tetracyclic pyrano[2,3,4‐de]chromenes from two very simple starting materials (an ortho‐alkynylsalicylaldehyde and an alkynamine or alkynol) with complete atom economy and with selective formation of bonds, cycles, and stereocenters. 相似文献
A concise and flexible synthesis of fully substituted 2‐aminopyrroles via gold‐catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles has been developed. Under mild reaction conditions, various 2‐aminopyrrole derivatives were obtained in good to excellent yields, thus providing an efficient and atom‐economic way for the construction of fully substituted 2‐aminopyrroles. 相似文献
Gold(I)-catalyzed formal [4+2] cycloaddition of O-aryl ynol ethers 1 and enol ethers 2 is described. This intermolecular reaction between two electron-rich unsaturated systems takes place, under mild conditions, in the presence of 5 mol% [IPrAu(CH3CN)]SbF6 as catalyst giving chromene derivatives with good yields. The cycloaddition is completely regio- and stereoselective, as well as versatile for both reactives. Silyl enol ethers can also react in the same way and under the same reaction conditions with quantitative yields. A plausible mechanism through a selective addition of the enol ether to the alkyne gold activated complex followed by an intramolecular aromatic electrophilic substitution is proposed. Several experimental results support the presence of a cationic oxonium intermediate prior to the aromatic substitution. The reaction represents a new entry to the chromene core. 相似文献
Efficient at room temperature : The Au complex generated in situ from [(IPr)AuCl] and AgSbF6 promotes the [4C+3C] intramolecular cycloaddition of allenes and dienes at room temperature, and in a particularly efficient and versatile manner. A DFT study on dimethylallenyl precursors agreed with the formation and cycloaddition of a metal–allyl cation intermediate, and points to the 1,2‐hydride shift as the key rate‐limiting step.
The Sc(OTf)3‐catalyzed [3+2] cycloaddition of allylsilanes to β‐silyl‐α,β‐unsaturated ketones (β‐silylenones) has been developed to form five‐membered syn‐1,3‐disilylketones diastereoselectively through the rearrangement of the silicon substituents on the allylsilane. Stabilization of the carbocation intermediates by a double silicon effect plays a key role in directing the course of the reaction to favor the [3+2] cycloaddition pathway over simple allylation. 相似文献
A synthetic method to stereoselectively prepare 4‐(cyclohexa‐1,3‐dienyl)‐1,3‐dioxolanes in good to excellent yields by gold(I)‐catalyzed [2+2+1] cycloaddition of 1,6‐diyne carbonates and esters with aldehydes is described. The cascade process involves 1,2‐acyloxy migration followed by cyclopropenation and cycloreversion. This leads to an unprecedented [2+2+1] cycloaddition of the resulting alkenylgold carbenoid species, examples of which are extremely rare, with two aldehyde molecules at catalyst loadings as low as 1 mol %. The usefulness of this cycloisomerization chemistry was further demonstrated by the transformation of one example to the corresponding phenol. 相似文献
Gold and rings : The gold(I)‐catalyzed addition of aldehydes to 1,6‐enynes gives 1,3‐dienes, by a cycloaddition/fragmentation process. 1,5‐Enynes react with aldehydes and ketones by the 5‐endo‐dig pathway to give the corresponding cycloadducts.
The [2+2+2] intermolecular carbocyclization reactions between 1,6‐enynes and alkynes catalyzed by [RuCl(cod)(Cp*)] (cod=1,5‐cyclooctadiene, Cp*=pentamethylcyclopentadienyl) are reported to provide bicyclohexa‐1,3‐dienes. The presented reaction conditions are compatible with internal and terminal alkynes and the chemo‐ and regioselectivity issues are controlled by the presence of substituents at the propargyl carbon center of the alkyne(s) partner(s). 相似文献
Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H‐azirine species afford pyrrole products with two regioselectivities when the Cβ‐substituted 2H‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H‐benzo[d]azepine products instead. 相似文献