Palladium-Catalyzed Ring Expansion Reaction of (<i>Z</i>)-1-(1,3-Butadienyl)cyclobutanols with Aryl Iodides. Stereospecific Synthesis of (<i>Z</i>)-2-(3-Aryl-1-propenyl)cyclopentanones

“…[60] Shibasaki and co-workers exploited a cascade asymmetric Heck reaction-carbanion capture process in order to synthesize various capnellenols and for the total synthesis of capnellene. When the Pd-catalyzed cascade insertion-ring expansion involve 1,3-dienylcyclobutanols and aryl iodides, various substituted cyclopentanones were synthesized in a stereospecific manner, as shown in Scheme 47.…”

Section: Conjugated Dienes and The Heck Reactionmentioning

confidence: 99%

Functionalized 1‐Alkoxy‐1,3‐dienes: Their Preparation and Applications in Synthetic Organic Chemistry

et al. 2006

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The reaction of various α,β‐unsaturated acetals with two equivalents of the Schlosser reagent LIC‐KOR [equimolar mixture of BuLi (LIC), and tBuOK (KOR)] gives 1‐metalated (1E)‐1‐alkoxy‐1,3‐dienes. These products can be transformed into trienic derivatives that are apt to participate in intramolecular Diels–Alder (IMDA) cycloaddition reactions, and can also be transformed into bifunctional (γ‐halo‐α‐carbonyl) reagents. Moreover, the metalated dienes can be readily functionalized with suitable electrophiles to afford products that have been found to be useful reagents for the Stille and Suzuki cross‐coupling reactions or arylated according to the conditions of the Heck process. Other significant syntheses of dienic and polyenic structures are reported along with some of their applications in organic synthesis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…Several cascade reactions carried out in the presence of a palladium or ruthenium catalyst have been developed [68][69][70][71][72][73][74] and a novel cascade reaction forming cyclic carbonates has been further devised, as depicted in Chart 22. When propargylic carbonate 104 was treated with p-methoxyphenol in the presence of a catalytic amount of zero valence of palladium catalyst under an Ar atmosphere, cyclic carbonate 105 was obtained together with dihydrofuran 106 and epoxide 107.…”

Section: Cascade Reaction Under Transition Metal-catalyzed Conditionsmentioning

confidence: 99%

Syntheses of Biologically Active Natural Products and Leading Compounds for New Pharmaceuticals Employing Effective Construction of a Polycyclic Skeleton

Ihara

2006

CHEMICAL & PHARMACEUTICAL BULLETIN

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IntroductionWhen various functional groups exist on a polycyclic skeleton, the three-dimensional relationships of the functional groups are restricted and a specific biological activity would be expected due to the rigid conformation (Chart 1). Therefore the development of an efficient method for the construction of polycyclic ring systems is highly desirable, particularly in the field of medicinal chemistry. Cascade reactions 2-7) forming a number of bonds in one operation are useful for the creation of polycyclic compounds. Many stereogenic centers can be created at the same time. A reduction in the number of reaction steps save reagents and energy and reduce waste. Therefore cascade reactions are important from the economic and green chemistry points of view. In this context, we have been studying cascade reactions under various reaction conditions, such as pericyclic, polar, radical, and transition metal-catalyzed reaction conditions. Cascade Reaction under Polar Conditions 2.1. Double Michael ReactionThe bicyclo[2.2.2]octane skeleton is a framework of several natural products. We encountered difficulty in the stereoselective synthesis of the corresponding polycyclic systems using the intramolecular Diels-Alder reaction.8) The problem was solved by employing the intramolecular double Michael reaction, as shown in Chart 2. The treatment of cyclohexenones 1 and 3 with an a,b-unsaturated ester side chain at the 6 or 5 position with LiN(TMS) 2 provided the polycyclic bridged compounds 2 and 4 in highly stereoselective manners, respectively. 9,10) The objective products were produced via ideal transition states, fixed by the coordination with lithium ion.As a typical example of the application of this methodology, the synthesis of (Ϯ)-culumorin (13) 11) is shown in Chart Cascade reactions are useful methods for the construction of polycyclic skeletons, which are important cores for biological activities. A variety of cascade reactions carried out under multiple reaction conditions, such as pericyclic, polar, radical, and transition metal-catalyzed reaction conditions, have been investigated. Culmorin, pentalenene, pentalenic acid, deoxypentalenic acid, longiborneol, cedrandiol, 8,14-cedranoxide, atisirene, atisine, and estrane-type steroids were synthesized via the intramolecular double Michael reaction. Aza double Michael reaction was applied to the syntheses of tylophorine, epilupinine, tacamonine, and paroxetine. Furthermore, sequential Michael and aldol reactions were performed in both intramolecular and intermolecular manners, leading to the formation of polycyclic compounds fused to a four-membered ring. Synthesis of paesslerin A utilizing a multicomponent cascade reaction revealed an error in the proposed structure. Unique cascade reactions carried out under radical and transition metal-catalyzed reaction conditions were also investigated. With the combination of several cascade reactions, serofendic acids and methyl 7b b-hydroxykaurenoate, both of which have neuroprotective activity, were synthesized in a...

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Palladium-Catalyzed Ring Expansion Reaction of (Z)-1-(1,3-Butadienyl)cyclobutanols with Aryl Iodides. Stereospecific Synthesis of (Z)-2-(3-Aryl-1-propenyl)cyclopentanones

Cited by 39 publications

References 43 publications

Ring Expansion of Cyclobutylmethylcarbenium Ions to Cyclopentane or Cyclopentene Derivatives and Metal-Promoted Analogous Rearrangements

Ring Expansion of Cyclobutylmethylcarbenium Ions to Cyclopentane or Cyclopentene Derivatives and Metal-Promoted Analogous Rearrangements

Functionalized 1‐Alkoxy‐1,3‐dienes: Their Preparation and Applications in Synthetic Organic Chemistry

Syntheses of Biologically Active Natural Products and Leading Compounds for New Pharmaceuticals Employing Effective Construction of a Polycyclic Skeleton

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