Palladium‐Catalyzed Directed meta ‐Selective C−H Allylation of Arenes: Unactivated Internal Olefins as Allyl Surrogates

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Section: Monodentate N-based Groupsmentioning

confidence: 99%

Decoding Directing Groups and Their Pivotal Role in C−H Activation

Murali

Machado

Carvalho

et al. 2021

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“…[a] Yields are reported as isolated; ( m /o)= meta /others determined by 1 H NMR analysis. [b] Mentioned based on previous report …”

Section: Figurementioning

confidence: 99%

“…Notably, the aryl sulfonyl scaffold produced mono‐ meta ‐allylation ( 10 a , 20:1) compared to thermal selectivity of 13:1 with completely unactivated symmetrical internal olefin, 4‐octene. Clear advantages of sonication over thermal reaction condition developed earlier in our laboratory were observed …”

Section: Figurementioning

confidence: 99%

Ultrasound‐Facilitated Direct meta‐C−H Functionalization of Arenes: A Time‐Economical Strategy under Ambient Temperature with Improved Yield and Selectivity

Jayarajan

Chandrashekar

Dalvi

2020

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The horizon of ultrasound‐assistance has been expanded to palladium‐catalyzed distal C−H functionalization of arenes. Compared to thermal conditions, operationally simple ultrasound mediated distal C−H functionalization occurred with a shorter reaction time and enhanced reactivity of reactants to give superior yields with improved selectivity both in terms of meta:others and mono:di. A wide variety of meta‐functionalizations such as olefination, alkylation, acetoxylation, allylation and cyanation were successfully carried out under ambient temperature.

“…Our initial efforts were focused on the pyrimidine‐based template, which has recently been used for different meta ‐selective C−H functionalizations . Model substrate 1 a (X= m ‐Me) with the benzylsulfonyl unit and perfluorohexene as the coupling partners were selected to perform our initial investigations.…”

Section: Figurementioning

confidence: 99%

Direct meta‐C−H Perfluoroalkenylation of Arenes Enabled by a Cleavable Pyrimidine‐Based Template

Brochetta

Borsari

Bag

et al. 2019

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The development of efficienta nd mild methods for the synthesis of organofluorine compounds is of foremost interest in various fields of chemistry.Adirect pyrimidine-based selective meta-CÀHp erfluoroalkenylationo f arenes involving several commerciallya vailable perfluoroolefins is described. The synthetic versatility of the protocol is demonstrated by an extensive substrate scopei ncludingd ifferent benzylsulfonyl, alkylarene and phenylacetic acid scaffolds. The generality of this methodology includingt he meta-CÀHp erfluoroalkenylation of Ibuprofen, the facile cleavageo ft he directing group and gram-scale reactions are presented.Fluorine-containingc ompounds are knownt op lay ap ivotal role in pharmaceutical/medicinal chemistry,b ut also in agrochemicala nd material sciences.F luorinea nd in particular the incorporation of CÀFb onds into organic molecules strongly influence their properties such as thermals tability,h igh chemical inertness ands olubility in organic solvents. [1] Bioavailability and metabolic stabilitya re commonlyi ncreased by substitution with fluorine atoms. [2] Alkenes and aromatic moieties bearing perfluorinated tails are widely used as as table isosterica nd isoelectronic mimics of the amide bond, and bioisosteres in structure-activity relationships tudies. [3] Althougho fg reat importance,t he synthesiso fp erfluoroalkenylated arenes through the incorporationo ff luoroalkyl chains has remained an out-standingc hallenge. Few strategies for the preparation of these structuralm otifs, such as the classical cross-couplingr eaction have been shown to be effective. [4,5] The existing methods usually require prefunctionalization of substrates or employment of non-readilya vailable starting materials, and these methods often suffer from low regio-or stereoselectivity and poor functionalg roup toleranced ue to the employmento fs ensitive reagents. [6] Therefore, new synthetic strategies featuring high efficiency and mild conditions are highly desirable.Over the past decades, transition-metal-catalyzed CÀHb ond functionalization has been establisheda sa ne ffectives trategy in late-stage functionalization of pharmaceuticals and bioactive molecules. [7] To achieve site-selective CÀHb ond functionalization at ad esired position, directing group (DG) approaches [8] have been employede xtensively for the ortho-CÀHb ond, [9] whereasd istal meta-a nd para-CÀHb onds have been much less addressed. In the past few years, meta-selective CÀHf unctionalizations of arenes have been accomplishedb ye xploiting the inherent steric and electronic properties of substrates, or by designing suitablet emplates. [10] In this context, direct CÀH perfluoroalkenylation of arenes is an important route in terms of both atom and step economy.V ery recently,L oh, Wang, and Ackermann elegantly reported ortho-CÀHf luoroalkenylation of arenest hrough CÀFb ond activation. [11] Intriguingly,t he metafunctionalization of arenes using sterically demanding electrophilic perfluoroalkenes remainsad ifficult task, due to th...