Pd-catalyzed borylative cyclisation of 1,7-enynes

Pardo‐Rodriguez, Virtudes; Buñuel, Elena; Collado‐Sanz, Daniel; Cárdenas, Diego J.

doi:10.1039/c2cc34468h

Cited by 55 publications

(14 citation statements)

References 42 publications

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“…On the other hand, enynes constitute versatile starting materials for the formation of carbo and heterocycles, 2 skeletal rearrangements, 3 and alkoxy-cyclisation, 4 among other reactions. During the last few years, Pd-catalyzed borylative cyclisation reactions of polyunsaturated species have been developed by our group [5][6][7][8][9] and Bäckvall's group, 10 with the aim of preparing cyclized boronates. Our seminal work described an unprecedented preparation of homoallylic boronates starting with 1,6-enynes, in which esters substituting the allylic position were tolerated (Scheme 1, top).…”

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confidence: 99%

Ligand-controlled divergent formation of alkenyl- or allylboronates catalyzed by Pd, and synthetic applications

et al. 2014

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The use of different ligands allows the preparation of either allyl-or alkenylboronates by Pd-catalyzed borylation of allylic carbonates containing alkyne groups. Unprecedented borylative cyclisation to alkenylboronates takes place with PCy 3 . The difficult dissociation of NHC ligands allows borylation of carbonates in the presence of alkynes. Oxidation, regioselective Suzuki coupling, as well as Au-catalyzed cycloisomerisation of boronates illustrate the potential synthetic applications of these reactions.Boronates are important synthetic reagents. They are stable and compatible with most functional groups and are environmentally friendly, tolerating oxygen and water. A wide variety of boronates can be used as nucleophilic partners in Suzuki cross-coupling reactions and allylboronates are reactive towards aldehydes and imines, just to cite the most common uses of these compounds. 1 For this reason, the development of methods for the preparation of boronates, avoiding the use of highly nucleophilic and basic reagents is of main interest. On the other hand, enynes constitute versatile starting materials for the formation of carbo and heterocycles, 2 skeletal rearrangements, 3 and alkoxy-cyclisation, 4 among other reactions. During the last few years, Pd-catalyzed borylative cyclisation reactions of polyunsaturated species have been developed by our group 5-9 and Bäckvall's group, 10 with the aim of preparing cyclized boronates. Our seminal work described an unprecedented preparation of homoallylic boronates starting with 1,6-enynes, in which esters substituting the allylic position were tolerated (Scheme 1, top). 5,11 In our previous studies, addition of ligands precluded the incorporation of the boron substituent. Now, we have found conditions in which the choice of the appropriate ligand allows control of the borylation of alkyne-containing allylcarbonates, affording simple Miyaura coupling to allylboronates, or unprecedented formation of alkenylboronates by borylative cyclisation, a method which is complementary to alkyne hydroboration and the usual reactions of strongly basic Li and Mg nucleophiles with B(OMe) 3 .Thus, we started our study by reacting enynes containing an allylic carbonate group (1). In our previous work mentioned above, 5 we reported that reactions of acetates or other ester derivatives, under ligandless conditions, took place without activation of the C-O bond, leading to homoallylic boronates containing the unreacted ester group (Scheme 1, top). Reactions in the presence of phosphines led to simple cycloisomerisation without incorporation of the boryl group.In contrast, reaction of carbonates 1a-l with B 2 (pin) 2 in the presence of Pd(OAc) 2 and the IMes ligand (formed in situ by deprotonation of the imidazolium chloride with t-BuOK) in xylene, afforded the corresponding allylboronates (Table 1). The reaction is fast (less than 30 min) and takes place under optimum conditions (50 1C) in the absence of added base, as usual for carbonates. A variety of starting compounds showing different ...

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Ligand-controlled divergent formation of alkenyl- or allylboronates catalyzed by Pd, and synthetic applications

et al. 2014

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“…Borylative cyclization in the presence of methanol, which generates a palladium hydride, gives access to six-membered cyclic compounds with incorporation of a single boron. 70 Enantioenriched quinolinones can be obtained by enantioselective hydroboration with concomitant cyclization using a cobalt catalyst with chiral phosphine ligands (94-99% ee) (Scheme 22). 71…”

Section: Cyclization 17-enynesmentioning

confidence: 99%

Silylboranes as Powerful Tools in Organic Synthesis: Stereo- and Regioselective Reactions with 1,n-Enynes

Moberg

2020

Synthesis

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Bismetalated alkenes, accessible by element–element addition to alkynes, are valuable building blocks in organic synthesis, providing wide opportunities for divergent synthesis. Silaboration of alkynes with a pendant olefinic group, catalyzed by group 10 metal complexes, and subsequent transformation of the silicon and boron functional groups give access to densely functionalized 1,3-dienes and 1,3,5-trienes with defined stereo- and regiochemistry, 1,2-dienes, and carbocyclic and heterocyclic products.1 Introduction2 Background3 Reactions with 1,3-Enynes4 Cyclization 1,6-Enynes5 Cyclization 1,7-Enynes6 Cyclization of 1,n-Enynes (n > 7)7 Cyclization of Dienynes and Enediynes8 Cyclization of 1,6-Diynes9 Conclusions

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“…The reaction could be extended to 1,7‐enynes . In this case, Pd trifluoroacetate had to be used as the catalyst, because Pd(OAc) 2 gave poorer results (Scheme ).…”

Section: Borylative Cyclization Involving the Formation Of C–c Bondsmentioning

confidence: 99%

Borylative Cyclization Reactions

Buñuel

Cárdenas

2016

Eur J Org Chem

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Borylative cyclizations constitute a family of important cascade reactions for the formation of carbo‐ and heterocycles containing boryl substituents. These compounds are formed from a variety of starting mono‐ and polyunsaturated substrates in metal‐catalyzed or boron‐mediated processes, and can be employed in subsequent functionalization. Here we review recently reported borylative cyclization reactions with special emphasis on metal‐catalyzed processes. These may involve the formation of one or several rings and the formation of a C–B bond in a domino process taking place within the same synthetic operation.

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Pd-catalyzed borylative cyclisation of 1,7-enynes

Abstract: Reaction of a variety of 1,7-enynes with bis(pinacolato) diboron catalysed by Pd bis(trifluoroacetate) affords homoallylic and allylic boronates containing a six membered carbo- or heterocycle, by formation of C-C and C-B bonds.

Cited by 55 publications

References 42 publications

Ligand-controlled divergent formation of alkenyl- or allylboronates catalyzed by Pd, and synthetic applications

Ligand-controlled divergent formation of alkenyl- or allylboronates catalyzed by Pd, and synthetic applications

Silylboranes as Powerful Tools in Organic Synthesis: Stereo- and Regioselective Reactions with 1,n-Enynes

Borylative Cyclization Reactions

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