Hypervalent iodine reagents constitute an essential tool in synthetic organic chemistry, promoting several different transformations efficiently.1 Our research group has been investigating rearrangement reactions, like ring contractions and ring expansion. Recently, we start to study the electrophilic alkynylation of ketones and aldehydes. Herein we describe some contributions in these works.Ring contraction reaction is a strategic transformation for the synthesis of indane derivatives, including the chemical synthesis of (+)-mutisianthol, (+)-trans-trikentrin A, and (�)-indatraline.2,3 Using chiral hypervalent iodine(III) compounds, which were generated in situ, we are now able to make the ring contraction of 1,2-dihydronaphthalenes asymmetrically, preparing indanes in good yield and ee.The synthesis of molecules bearing seven- and eight-membered rings can be performed by ring expansion of 1-vinylcycloalkanols (or the corresponding silyl or methyl ether) and heterocyclic benzo-methylenes mediated by the hypervalent iodine reagent HTIB (PhI(OH)OTs). Reaction conditions can be easily adjusted to give seven- and eight-membered rings bearing different functional groups.The electrophilic a-alkynylation of ketones and aldehydes was developed using TMS-EBX under mild conditions. Carbonyl compounds bearing an a-acetylene group were obtained in good to excellent yields.4Selected References:1. L. F. Silva, Jr, B. Olofsson, �Hypervalent Iodine Reagents in the Total Synthesis of Natural Products� Natural Product Reports 2011 , 28, 1722.2. L. F. Silva, Jr, �Adventures in Ring Contraction Reactions�, Synlett 2014 , 25, 466.3. I. R. M. T�b�ka, G. B. Longato, M. V. Craveiro, J. E. de Carvalho, A. L. T. G. Ruiz, L. F. Silva Jr, �Total Synthesis of (+)-trans-Trikentrin A�, Chemistry � A European Journal 2012 , 18, 16890.4. A. Utaka, L. N. Cavalcanti, L. F. Silva, Jr, �Electrophilic Alkynylation of Ketones Using Hypervalent Iodine�, Chemical Communications 2014 , 50, 3810.

Hypervalent iodine in synthetic organic chemistry: Electrophilic alkynylation and rearrangement reactions

248th National Meeting (2014)

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