When gold can do what iodine cannot do: A critical comparison

Abstract

SummaryGold catalysis has emerged as one of the most dynamic fields in organic synthesis. Only recently, more and more domino processes, for which gold pre-catalysts were found to be outstandingly effective, were paralleled by employing iodine electrophiles in place of gold compounds. This review highlights how, in certain cases, iodonium activation can match gold-catalyzed reactions to construct identical product scaffolds. Likewise, processes are discussed where mostly identical starting materials are transformed into diverse frameworks depending on whether gold or iodonium activation was used to trigger the reaction.

Intramolecular Iodine‐Mediated Oxygen Transfer from Nitro Groups to C≡C Bonds

“…In almost all cases electrophilic cyclization results in incorporation of iodine in the final product, [13] whereas gold catalysis typically results in hydrogen at the same position, due to the protodeauration step required for catalyst regeneration. [15,16] The method presented here is a unique example of iodine-mediated ring closure of internal alkynes with-out the introduction of halogen or oxygen from the solvent into the newly formed ring. Moreover, the developed method can be used broadly for the preparation of fused isoxazoles through nitro-alkyne cycloisomerization of either electron-rich or electron-poor substrates.…”

Gold‐Catalyzed Synthesis of Iodofulvenes

“…Dichloromethane was then added and the mixture was washed with brine. The organic layer was dried over MgSO 4 3432,3087,2967,2864,2603,2222,1599,1558,1508,1463,1395,1349,1254,1221,1120,1033,1004,913,860,830,750,735,702,664,612,543,526,436 3066,2923,2901,2863,1706,1600,1461,1433,1199,917,758,708…”

“…[3] Iodine has also attracted considerable attention as a p-activator, and there is an astonishing parallel reactivity between iodine and gold. [4] This leads to a series of useful transformations in which iodine (as a stoichiometric reagent) can replace gold as an electro-philic activator, giving rise to the corresponding iodinated derivatives. On the basis of this evident similarity between gold and iodine, we were curious as to whether iodine is also able to play a role in the new field of s/p dual-activation chemistry (Scheme 1).…”

“…From diyne starting materials, a series of interesting products can be obtained through intramolecular2 and intermolecular reactions 3. Iodine has also attracted considerable attention as a π‐activator, and there is an astonishing parallel reactivity between iodine and gold 4. This leads to a series of useful transformations in which iodine (as a stoichiometric reagent) can replace gold as an electrophilic activator, giving rise to the corresponding iodinated derivatives.…”

Synthesis and application of gold-carbon hybrids as catalysts for the hydroamination of alkynes

“…Hydroamination reactions enable the synthesis of nitrogen-containing organic compounds which are widely present in the nature and provide biological-and pharmaceutical activity [29], and can be used in cosmetics as well as intermediates in many industrial processes and in the synthesis of agrochemical products [30]. The conventional synthesis routes to obtain C-N bond-containing molecules are however limited, hence it is of great importance the development of methods to catalytically add a nucleophile nitrogen to a C-C multiple bond [31,32]. Gold-containing complexes and the catalysis of hydroamination reactions avoids the use of acidic media and the formation of by-products in very regioselective hydroamination reactions [11,35].…”