Acylated amino acid ligands enabled ruthenium(II)-catalyzed C-H functionalizations with excellent levels of meta-selectivity. The outstanding catalytic activity of the ruthenium(II) complexes derived from monoprotected amino acids (MPAA) set the stage for the first ruthenium-catalyzed meta-functionalizations with removable directing groups. Thereby, meta-alkylated anilines could be accessed, which are difficult to prepare by other means of direct aniline functionalizations. The robust nature of the versatile ruthenium(II)-MPAA was reflected by challenging remote C-H transformations with tertiary alkyl halides on aniline derivatives as well as on pyridyl-, pyrimidyl-, and pyrazolyl-substituted arenes. Detailed mechanistic studies provided strong support for an initial reversible C-H ruthenation, followed by a SET-type C-Hal activation through homolytic bond cleavage. Kinetic analyses confirmed this hypothesis through an unusual second-order dependence of the reaction rate on the ruthenium catalyst concentration. Overall, this report highlights the exceptional catalytic activity of ruthenium complexes derived from acylated amino acids, which should prove instrumental for C-H activation chemistry beyond remote functionalization.

Diaryl ethers are common structural features in numerous natural products and biologically active compounds. Despite more than a century of immense focus on finding efficient synthetic routes to this compound class, diaryl ethers remain difficult to obtain. Routes that are catalytic in copper have been developed, but high catalyst loadings, excess reagents, elevated temperatures and long reaction times are still needed. Pd-catalyzed cross-couplings of phenols and aryl halides at temperatures up to 100 °C have recently been reported to give high yields of diaryl ethers. Diaryliodonium salts are non-toxic alternatives to transition metals in the synthesis of diaryl ethers and we have recently developed effective synthetic routes to these salts.Herein we report a fast, high-yielding synthesis of diaryl ethers. The reaction conditions are mild, metal-free, and avoid the use of halogenated solvents, additives, or excess reagents. Precautions to avoid air or moisture are not needed. The scope includes ortho-and halo-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols . Monday,

Um protocolo livre de metais foi desenvolvido para sintetizar indanos através da contração de anel de 1,2-di-hidronaftalenos promovida por PhI(OH)OTs (HTIB ou reagente de Koser). Este rearranjo oxidativo pode ser realizado em diversos solventes (MeOH, CH 3 CN, 2,2,2-trifluoroetanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), e uma mistura 1:4 de TFE:CH 2 Cl 2 ) em condições brandas. A contração de anel fornece indanos trans-1,3-dissubstituídos diastereosseletivamente, os quais são difíceis de obter em química orgânica sintética.A metal-free protocol was developed to synthesize indanes by ring contraction of 1,2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser's reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH 3 CN, 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH 2 Cl 2 ) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1,3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry.Keywords: indanes, hypervalent iodine, ring contraction, 1,2-dihydronaphthalenes, rearrangements IntroductionThe indane ring system is present in several natural products and in non-natural compounds with remarkable biological activity.1 Consequently, efforts have continuously been made to develop new routes to obtain molecules with this unit.2 A typical strategy to synthesize a functionalized indane is by selecting an appropriate indanone, which is then elaborated into the target molecule. 2,3 As tetralones are usually cheaper than indanones, the preparation of indanes starting from a tetralone (or a derivative) through a ring contraction rearrangement could be advantageous. 4 In the last years, hypervalent iodine reagents have become an essential tool in synthetic organic chemistry due to the plethora of reactions that can be performed with them in excellent yield and selectivities. 5 Moreover, hypervalent iodine compounds represent in many cases an alternative to toxic heavy metals. 5 Although the oxidative rearrangement of alkenes mediated by iodine(III) has been described in some papers, 6 the ring contraction of 1,2-dihydronaphthalenes was reported for a few substrates using only p-Me-C 6 H 4 -IF 2 , 6 which led to fluorinated indanes.Herein, we describe an efficient metal-free protocol for the synthesis of indanes under mild conditions. In a preliminary communication, we report the ring contraction of 1,2-dihydronaphthalenes (which are obtained from 1-tetralones) mediated by PhI(OH)OTs (HTIB or Koser's reagent) for a few substrates. 7 In this article, the oxidation of several additional substrates is presented, better defining the reaction scope. Additionally, other reaction conditions were Metal-Free Synthesis of Indanes by Iodine(III)-Mediated Ring Contraction J. Braz. Chem. Soc. 1796 discovered using fluoroalcohols as solvent, which highly improved isolated yields. The best condition employed a 4:1 mixture of CH 2 Cl 2 -TFE that led to indanes in...

A diastereoselective route to (+)-bakkenolide A is presented from the readily available optically active Wieland-Miescher ketone. This novel synthesis of this sesquiterpene lactone features the following as key stereoselective transformations: (i) the ring contraction reaction of a octalone mediated by thallium(III) nitrate (TTN); (ii) a hydrogenation to create the cis-fused junction; and (iii) the formation of the C7 quaternary center through an enolate intermediate. Furthermore, during this work, the absolute configuration of a trinorsesquiterpene isolated from Senecio humillimus was assigned.