450412-21-2Relevant academic research and scientific papers
Ring opening of aziridines with ortho-bromophenyl metal reagents: synthesis of 2-substituted indolines
Michaelis, David J.,Dineen, Thomas A.
body text, p. 1920 - 1923 (2009/08/17)
Stabilized ortho-bromo phenyllithium reagents, generated via lithium-halogen exchange of aryl iodides, undergo regioselective ring opening of mono-substituted N-Boc, N-Cbz, and N-tosyl-protected aziridines in good to excellent yields. The resulting ortho-
Generation and suppression of 3-/4-functionalized benzynes using zinc ate base (TMP-Zn-ate): New approaches to multisubstituted benzenes
Uchiyama, Masanobu,Kobayashi, Yuri,Furuyama, Taniyuki,Nakamura, Shinji,Kajihara, Yumiko,Miyoshi, Tomoko,Sakamoto, Takao,Kondo, Yoshinori,Morokuma, Keiji
, p. 472 - 480 (2008/10/09)
We present full details of our new methods for preparing functionalized benzynes with lithium di-alkyl(2,2,6,6-tetramethylpiperidino)zincate (R 2Zn(TMP)Li) through deprotonative zincation as a key reaction. In this system, by choosing appropriate ligands for the zincate, either regioselective zincation of functionalized haloaromatics or the generation of substituted benzynes can be controlled in good yields with excellent chemoselectivity, using the same substrate. Zincation with tBu 2Zn(TMP)Li followed by electrophilic trapping or zincation with Me2Zn(TMP)Li followed by nucleophilic or diene trapping is shown to be a powerful tool for the chemoselective preparation of 1,2,3-/1,2,4- trisubstituted benzene derivatives. These methods offer far greater generality than previous methods for the synthesis of multifunctionalized benzenes. Computational/theoretical studies of the reaction mechanism of this unique benzyne formation indicated that preferential coordination of the dialkylzinc moiety of zincate to halogen is the reason for the reduced activation energy of the elimination, that is, for the formation of the benzyne. The role of the ligands on Zn in accelerating/decelerating the elimination is also discussed.
Direct ortho cupration: A new route to regioselectively functionalized aromatics
Usui, Shinya,Hashimoto, Yuichi,Morey, James V.,Wheatley, Andrew E. H.,Uchiyama, Masanobu
, p. 15102 - 15103 (2008/09/17)
We have developed a direct regio- and chemoselective method for generating functionalized aromatic cuprate compounds through deprotonative directed ortho cupration using TMP(tetramethylpiperidino)-cuprates (R(TMP)Cu(CN)Li2; R = alkyl, phenyl, o
Generation of functionalized asymmetric benzynes with TMP-zincates. Effects of ligands on selectivity and reactivity of zincates
Uchiyama, Masanobu,Miyoshi, Tomoko,Kajihara, Yumiko,Sakamoto, Takao,Otani, Yuko,Ohwada, Tomohiko,Kondo, Yoshinori
, p. 8514 - 8515 (2007/10/03)
We have developed new methods for preparing functionalized benzynes through deprotonative zincation as a key reaction using R2Zn(TMP)Li, and we also describes dramatic ligand effects on the benzyne formation. Deprotonative zincation of various meta-substituted bromobenzenes with Me2Zn(TMP)Li proved effective for the one-pot generation of various 3-functionalized benzynes, particularly those electrophilic substituents such as ester, amide, and cyano. On the other hand, zincation with tBu2Zn(TMP)Li, followed by electrophilic trapping (with I2) proved a powerful tool for the preparation of 1,2,3-trisubstituted aromatic compounds.8 The resultant 1,2,3-trisubstituted benzenes are available as precursors for generation of 3-substituted benzynes by halogen-zinc exchange reactions with Me3ZnLi. These methods offer far greater generality than previous methods for the synthesis of functionalized asymmetric benzynes, and should be of value in new syntheses of various natural products and functional materials. In addition, these results underline the utility of spectator ligands on the central metal of ate complexes as a tunable functionality in the development of new ate complex-promoted reactions. Copyright
