Search

In this study, we report a Rh(I)/dppf catalytic system that can tune the regioselectivity of methylenecyclobutanes. Under the optimal reaction conditions, a series of 1,3‐disubstituted cyclobutanes were prepared in high yields (up to 95%) with excellent regioselectivity (>20:1 r.r.). Scale‐up synthesis of the cyclobutane product at a low catalyst loading (2 mol%) demonstrates the robustness of this dppf‐controlled hydroacylation. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Transition‐metal catalyzed C—C bond activation is a formidable challenge owing to the high bond energy. We report here a novel palladium‐catalyzed C—C bond activation manner of methylenecyclobutanes followed by subsequent Suzuki cross‐coupling reaction affording multisubstituted indanes. The tandem reaction process involves intramolecular carbopalladation of double bond, β‐carbon elimination and intermolecular trapping of the transient σ‐alkylpalladium complex with boronic acids. A new TADDOL‐derived phosphoramidite ligand bearing fluorine and silicon‐based bulky groups is found to be efficient for C—C bond activation of methylenecyclobutanes. [ABSTRACT FROM AUTHOR]

A highly diastereoselective synthesis of methylene-cyclobutanes possessing a quaternary stereocenter is reported, in which boron homologation of an easily-generated cyclobutenylmetal species is performed, followed by an allylation reaction. Combining three steps in a one-pot process further optimized the method, which afforded the expected adducts in excellent yields and stereoselectivity, starting from commercially available 4-bromobutyne. [ABSTRACT FROM AUTHOR]

[image omitted] Reactions of methylenecyclobutanes (MCBs) with NXS-H2O system were investigated. The results were quite different from that of methylenecyclopropanes (MCPs), and an interesting aryl-transfer reaction happened to give substituted cyclobutyl ketones as products when disubstituted MCBs were employed. When monosubstituted MCBs were employed, the direct halohydroxylation gave the cyclobutyl ring untouched adducts. All of these analogs have potential application value in organic synthesis. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. [ABSTRACT FROM AUTHOR]

Abstract: Methylenecyclobutanes undergo a lithiation reaction in the presence of n-BuLi or n-BuLi/KO t Bu from −78°C to room temperature or to 40°C in THF within 3h and then quenching with a variety of electrophiles to give the corresponding addition products (alcohols) in moderate to good yields within 2h. The alcohols can be easily oxidized to the ketones, which can be transformed to the substituted cyclopentenes in the presence of AlCl3 within short reaction time. [Copyright &y& Elsevier]

Abstract: Methylenecyclobutanes undergo an interesting rearrangement reaction in the presence of silver acetate and iodine at room temperature (20°C) in dichloromethane to give the corresponding aryl-(1-arylcyclobutyl)methanones in good to high yields within short reaction time. A plausible reaction mechanism has been discussed on the basis of control and O18-labeling experiments. [Copyright &y& Elsevier]

The stereochemical and mechanistic aspects of the degenerate thermal isomerizations available to deuterium-labeled Z-ethylidene-2-methylcyclobutanes remain incompletely defined. Relevant data and several conjectural readings of the data are reconsidered in light of current understandings of thermal stereomutations and [1,3] carbon sigmatropic shifts. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Treatment of aryl bromides with homoallyl alcohols bearing a trimethylene group at the allylic position in the presence of cesium carbonate under palladium catalysis affords (2-aryl�ethylidene)cyclobutanes selectively. The selective formation of the alkylidenecyclobutane skeleton results from regiospecific retro-�allylation of the homoallyl alcohols, which accompanies the transposition of the double bonds. [ABSTRACT FROM AUTHOR]