- Palauchlor: A practical and reactive chlorinating reagent
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Unlike its other halogen atom siblings, the utility of chlorinated arenes and (hetero)arenes are twofold: they are useful in tuning electronic structure as well as acting as points for diversification via cross-coupling. Herein we report the invention of a new guanidine-based chlorinating reagent, CBMG or "Palauchlor", inspired by a key chlorospirocyclization en route to pyrrole imidazole alkaloids. This direct, mild, operationally simple, and safe chlorinating method is compatible with a range of nitrogen-containing heterocycles as well as select classes of arenes, conjugated π-systems, sulfonamides, and silyl enol ethers. Comparisons with other known chlorinating reagents revealed CBMG to be the premier reagent.
- Rodriguez, Rodrigo A.,Pan, Chung-Mao,Yabe, Yuki,Kawamata, Yu,Eastgate, Martin D.,Baran, Phil S.
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supporting information
p. 6908 - 6911
(2014/06/09)
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- Electroreductive Dehalogenation of Chlorinated Aromatic Ethers. Unexpected Electrogenerated Base Catalyzed Reactions
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The electroreductive dehalogenation of several mono- and polychlorinated aromatic ethers that serve as models of dioxins has been studied.The dechlorination was achieved by a simple constant-current electrolysis using a lead cathode in dimethylformamide.It was shown that 2,4,6-trichloroanisole undergoes successive dechlorination and the chlorine in the 2-position is selectively eliminated.Competitive reactions and cyclic voltammetric measurements suggested the increasing reactivity order of mono- di- trichloride for the reductive dechlorination.Use of allyl 2-chloro phenyl ether as a probe for radical cyclization indicated that free radical intermediates are of little importance.Thus, incipient radicals are immediately reduced to anionic intermediates.The electrolyses in the presence of deuterium oxide revealed proton sources for the present dechlorination.In these attempts, novel phenomena due to electrogenerated base (EGB) were found: di- and trichlorides underwent an unexpected overincorporation of deuterium in their dechlorinated products; a selective formation of Z-enol ethers from the allylic ethers was encountered.The mechanistic features of the present electroreductive dechlorination are discussed.
- Kimura, Makoto,Miyahara, Hiroyoshi,Moritani, Noriyuki,Sawaki, Yasuhiko
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p. 3897 - 3902
(2007/10/02)
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