Carboindation of Carbon−Carbon Triple Bonds:  Regioselective Indium-Mediated Allylation of Functionalized Alkynes and Transformation into Halogen-Substituted 1,4-Dienes

Abstract

By examining the allylindation of a series of substituted alkynes, the relationships between allylindation reactivity and alkyne structure were systematically investigated. While terminal alkynes with protected hydroxyl groups gave the corresponding allylated branched 1,4-dienes (Markovnikov products) within 5-6 h, the unprotected alkynols reacted markedly faster, requiring only 2-4 h of ultrasonication in THF to produce the 1,4-dienols in good yields. In the latter reactions, the regioisomeric outcome was found to depend on the distance between the hydroxyl group and the alkyne moiety: propargylic substrates gave linear 1,4-dienes (anti-Markovnikov products), suggesting the involvement of bicyclic "chelation-controlled" transition state, while 4-pentynol and higher homologues exclusively afforded the branched 1,4-dienes. Moreover, the proposed vinylic R,R-bis-indium intermediates from both protected and unprotected substrates were successfully quenched with N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS) to form tri-and tetrasubstituted dienes in good yields. Taken as a whole, these results illustrate the remarkable stability of the allylindium and vinylindium intermediates despite the presence of protic functionalities in the reaction mixture.

Recent advances in allylindium reagents in organic synthesis

“…7a,b They carried out the reaction of allylindium reagents and unactivated alkynes in THF to obtain various 1,4-pentadienes in good-to-high yields. The Markovnikov product (vide infra) was obtained selectively and the involvement of a vinylic a,a-bis-indium intermediate A more systematic study on the carboindation of carbone carbon triple bonds was carried out by Klaps and Schmid in 1999, as shown in Scheme 4. 8 They found that unprotected alkynols reacted with allylindium reagents markedly faster, requiring only 2e4 h of ultrasonication in THF to produce the products in good yields.…”

“…The Markovnikov product (vide infra) was obtained selectively and the involvement of a vinylic a,a-bis-indium intermediate A more systematic study on the carboindation of carbone carbon triple bonds was carried out by Klaps and Schmid in 1999, as shown in Scheme 4. 8 They found that unprotected alkynols reacted with allylindium reagents markedly faster, requiring only 2e4 h of ultrasonication in THF to produce the products in good yields. In this reaction, the regioisomeric outcome was found to depend on the distance between the hydroxyl group and the alkyne moiety; propargyl alcohol gave the anti-Markovnikov product via the involvement of a bicyclic chelation-controlled transition state 5, while 4-pentynol and higher homologs exclusively afforded the branched 1,4-dienes, the Markovnikov products.…”

“…Araki and co-workers have reported a chelation-controlled regio-and stereoselective allylation of norbornenol derivatives. 12 The reaction of allylindium and syn-bicyclo [2.2.1]hept-2-en-7-ol (8) in THF at refluxing temperature afforded three products in moderate yields, whereas, the allylindation product was the major component (72%) in NMP (180 C). Under the latter conditions, iodinated and oxygenated products were not formed.…”

Ruthenium‐katalysierte Reaktionen – eine Schatzkiste für atomökonomische Umwandlungen

“…B. der formalen Synthese von (À)-Mycalamid A (190) (Schema 17). [148] In [158][159][160][161] eine Lewis-säurekatalysierte Addition von Allylsilanen oder Allylstannanen [162][163][164] oder auch eine Palladium-katalysierte Addition von Allylhalogeniden an Alkine. [165] 5.3.…”

Regioselective Addition of Allylindium Reagents to Allenes in Functionalized 1,6‐Diols Bearing Allenynes

“…[7] More recently, it was reported that allylation of unactivated terminal alkynes by treatment with allylindiums provided branched 1,4-dienes through regioselective Markovnikov addition.…”