Tris(4-bromophenyl)aminium Hexachloroantimonate-Initiated Oxidative Povarov-Type Reaction between Glycine Esters and (Cyclopropylidenemethyl)benzenes Using the Counterion as a Chlorine Donor

Abstract

A tris(4-bromophenyl)aminium hexachloroantimonate-initiated oxidative Povarov-type reaction between glycines and methylenecyclopropanes was realized in the presence of dioxygen, in which the counterion, SbCl 6 − , served as a chlorine atom donor, enabling the synthesis of a series of chlorinated quinolines in high yields. The mechanistic study showed that the chlorination step might be related to antimony chloride via a radical chlorine atom transfer.

Visible-Light-Induced Dehydrogenative Imidoylation of Imidazo[1,2-a]pyridines with α-Amino Acid Derivatives and α-Amino Ketones

“…Direct dehydrogenative cross-coupling has been considered as a promising ideal synthetic tool to construct new chemical bonds because this type of reaction avoids functional group interconversion and has the advantages of high atomic and step economy . Much attention has been paid for direct α-functionalization of the C–H bond in α-amino carbonyl compounds with various coupling partners to deliver α-substituted α-amino carbonyl derivatives in the past decade. , However, the use of α-amino carbonyl compounds to produce a new C–C or C–heteroatom bond and a C–N double bond has been rarely studied . For example, in 2012, Li’s group reported an oxidative α-arylation of α-amino carbonyl compounds with indoles to produce 2-(1 H -indol-3-yl)-2-iminocarbonyls using a CuCl/TBHP catalytic system .…”

Triarylamminium Radical Cation Facilitates the Deprotection oftert-Butyl Groups in Esters, Ethers, Carbonates, and Carbamates

“…The tris-4-bromophenylamminium cation radical (MB •+ ) is a commercially available reagent commonly used as a single-electron oxidant and/or an acid generator in various synthetic transformations, including protecting group removal ( para -methoxybenzyl ether, tetrahydropyranyl (THP) ether, dithioketal, and silyl ethers), glycosylations, and radical rearrangements, as well as in a high number of radical cation-mediated [4 + 2], [2 + 2], and [3 + 2] cycloaddition reactions . In addition, MB •+ has been shown to oxidize various tertiary amines, , electron-rich aromatics, − and enolates and to mediate Markovnikov hydration of ( E )-aryl enynes to the corresponding enones …”

The Povarov Reaction: A Versatile Method to Synthesize Tetrahydroquinolines, Quinolines and Julolidines

“…1,8 When no oxidizing agent is added to the reaction medium, O 2 (air) is the final oxidant. 14,136 Similarly to the synthesis of THQs, these reactions can be catalyzed by Lewis and Brønsted acids such as BF 3 •OEt 2 , 36,40,137-142 BF 3 •O(CH 3 ) 2 , 143,144 FeCl 3 , 145,146 InCl 3 , 147 trifluoromethanesulfonic acid, 148 p-toluenesulfonic acid, 146 CX4SO 3 H, 14,149 TFA, 150,151 camphorsulfonic acid, 152 tris(4-bromophenyl)aminium (TBPA + ), 140,[153][154][155] CBr 4 , 156 iron, 157 copper iodide 158 and iodine. [159][160][161][162][163][164][165][166][167] Furthermore, different triflates have been widely used such as Sc(OTf) 3 , 154,168,169 Yb(OTf) 3 , [170][171][172][173] Cu(OTf) 2 , 174,175 Ce(OTf) 3 , 176,177 Zn(OTf) 2 , 178 AgOTf, 22 In(OTf) 3 179 and Ca(OTf) 2 .…”