Synthesis of heterocycles from allenes containing electron-withdrawing substituents under the conditions of electrophili
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Synthesis of heterocycles from allenes containing electron-withdrawing substituents under the conditions of electrophilic activation: recent advances Stanislav V. Lozovskiy1* 1
Saint Petersburg State University, 26 Universitetsky Ave., Petergof, Saint Petersburg 198504, Russia; е-mail: [email protected]
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(7), 848–853
Submitted April 27, 2020 Accepted May 20, 2020
The review considers the latest advances in the synthesis of heterocyclic compounds based on the reactions of allenes containing electronwithdrawing substituents with electrophiles. The material is grouped by the type of electron-withdrawing fragment in the allenes: carbonyl, phosphine oxide, and sulfonyl/sulfinyl groups. The bibliography includes 28 literature sources. Keywords: acid, allene, electrophile, heterocycle, superacid.
The chemistry of allenes is currently undergoing a period of rapid development. A characteristic feature that attracts the attention of chemists is diverse and often unexpected reactivity of allenes.1 In addition, allene fragment is found in natural compounds2 and functional materials.3 Reactions of allenes containing electron-withdrawing substituents with electrophiles are an effective tool for the creation of heterocyclic systems. This review summarizes the latest advances in this area, dividing works by the type of electron-withdrawing fragment in allenes: carbonyl component C=O or its disguised variant CF2X (X = CnF2n +1, P(O)(OEt)OH), phosphine oxide component P=O, and sulfoxide component S=O, including in the sulfonyl group SO2R (Scheme 1).
Reactions of allenes containing C=O or CF2X group Perfluoroalkyl-1,2-allenyl ketones 1 in the presence of catalytic amounts of trifluoromethanesulfonic acid (TfOH) or AuCl participate in an intramolecular cyclization reaction, accompanied by the migration of the R1 substituent, forming furans 2 in 56–91% yields. Hydrolysis of compounds 2 with heating in the presence of TfOH and H2O leads to the formation of ketones 3 in 43–95% yields4 (Scheme 2). Scheme 2
Scheme 1
Allenes 4, that are formed as a result of the reaction of propargyl alcohols 5 and arenes upon promotion with 0009-3122/20/56(7)-0848©2020 Springer Science+Business Media, LLC
848
Chemistry of Heterocyclic Compounds 2020, 56(7), 848–853 Scheme 5
acidic reagents (TfOH or HUSY CBV-720 zeolite) can undergo intramolecular cyclization with the formation of aryl-substituted furanones 6 in the yields up to 90%5 (Scheme 3). Scheme 3
Highly unsaturated allenes 7 react with sulfonylhydrazides 8 in the presence of stoichiometric amounts of I2 and tert-butylhydroperoxide to form 3,4-dihydrophthalazines 9 in 40–80% yields. Iodine in this reaction is a multifunctional promoter: it produces electrophilic activation of the allene system by coordination to the C=O group, which triggers the (2+2) cycloaddition reaction, leading to the formation of cyclobutene 10, participates in the opening of intermediate 11, and is a leaving group during the final cyclization of c
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