Introduction of Allyl and Prenyl Side‐Chains into Aromatic Systems by Suzuki Cross‐Coupling Reactions

Abstract

This paper reports some studies aiming at the developement of a general protocol useful for the synthesis of allyl-and prenylaromatic compounds. The first part deals with the preparation of boron reagents like arylboronic acids and their pinacol esters as well as of pinacol allyl-and prenylboronates. The second part of the paper is devoted to the use of these boron reagents in Suzuki-Miyaura cross-coupling reactions leading to allylation and prenylation of aromatic compounds. Of the six methods studied, the most promising re- IntroductionThe selective formation of new carbon-carbon bonds is frequently a key step in the synthesis of molecules of high added value, like fine chemicals, as well as in the preparation of conventional and special polymers. Cross-coupling reactions catalysed by metal complexes could undoubtedly be included among the most powerful and versatile synthetic methods for achieving these transformations.[1] During the last 30 years, the development of a wide variety of cross-coupling methods has facilitated the synthesis of carbon-carbon bonds between unsaturated species, notably sp and sp 2 moieties, like vinyl, alkynyl and phenyl groups. Of the coupling reactions catalysed by palladium, the SuzukiMiyaura reaction, that is, the reaction between organoboron compounds and organic electrophiles, for example, vinyl, alkynyl, aryl and benzyl halides and triflates, catalysed by palladium complexes (Scheme 1) is one of the most useful for making carbon-carbon bonds.[2] The first example of this protocol was reported by Suzuki and coworkers in 1979. [3] Some of the advantages of this reaction are the availability of a wide variety of reagents, mild reaction conditions, the compatibility of boron derivatives with a wide range of functional groups and their lower toxicity compared with [a] other organometallic derivatives, for example, organotin compounds. In addition, inorganic boron byproducts have a low environmental impact, minimal toxicity and can be removed by very simple procedures. On the other hand, taking into account the fact that allylation and prenylation reactions are useful tools for the introduction of chains containing carbon-carbon double bonds leading to fragments that in many cases are part of natural products, [4,5] it would certainly be of interest to find more general techniques for carrying out these reactions. Although successful allylation and prenylation reactions of a wide variety of organic substrates by cross-coupling reactions have been reported, [5a,5b,6] in most cases the protocols of these reactions could only be applied with excellent yields to particular systems and not in general. Also, surprisingly, the nature of the organoboron coupling partners has been little studied. Owing to the importance of these reactions in synthetic applications, we considered it of interest to carry out a study to establish both the conditions and methods needed to develop a protocol that could be applied successfully to the allylation and prenylation of a wide number of organic substr...

Total synthesis of xiamenmycin C and all of its stereoisomers: stereochemical revision

“…The amide moiety of xiamenmycin C could be synthesized from substituted methyl benzoate 6 via hydrolysis and amidation [6,7], while the key intermediate 6 might be formed through a highly regio-and diastereoselective oxidative cyclization [8] from 5, which, in turn, could be accessed from organoboron 3 via Suzuki-Miyaura coupling [9,10].…”

“…Thus, treatment of neryl acetate 2 with bis(pinacolato)diboron (B 2 Pin 2 ) in the presence of catalytic amount of bis(1,5-cyclooctadiene)nickel(0) (Ni(cod) 2 ) and tricyclohexylphosphine (PCy 3 ) [9] afforded the organoboron 3, which was subjected to the Suzuki-Miyaura coupling with MOM-protected methyl 3-bromo-4-hydroxybenzoate using [1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (Pd(dppf)Cl 2 ) [10] as catalyst to give the benzoate Z-5 in good yield.…”

A Tribute to Prof. Julio César Podestá

“…19 He is also interested in the development of more efficient and versatile protocols for carrying out synthesis via cross-coupling reactions. 20 The results obtained by Julio's research group until present have resulted in the publication of 70 research articles and have also been reported in numerous national and international meetings and symposia. Julio has so far supervised eleven Doctor in Chemistry theses (two of them are currently in progress) and three Master theses; he has also been adviser of members of the research career of the National Research Council of Argentina (CONICET) and of many doctoral students.…”

Nickel-Catalyzed C-Br/C-H Bis-phenylation of Methyl 4-Bromocrotonate: A Stereoselective Entry to Methyl (E)-3,4-Diphenylbut-2-enoate

“…[7] Metal-catalyzed arylations of diverse electrophilic partners have been widely discussed in the literature. [8][9][10][11][12][13][14] In contrast, reports on bis-arylations are very rare and mainly restricted to aromatic electrophiles. [15][16][17][18][19] Polyarylated structures are an important class of organic compounds as they can find applications in various fields, including medicinal [20][21][22][23][24] and materials [25][26][27][28][29][30][31][32][33] chemistry.…”