Concerning the Structures of Alkali-Metal-Mediated ortho Zincation of Benzamides and Phenyl O-Carbamate

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• 作者：Liam Balloch ; Alan R. Kennedy ; Robert E. Mulvey ; Toni Rantanen ; Stuart D. Robertson ; Victor Snieckus
• 刊名：Organometallics
• 出版年：2011
• 出版时间：January 10, 2011
• 年：2011
• 卷：30
• 期：1
• 页码：145-152
• 全文大小：857K
• 年卷期：v.30,no.1(January 10, 2011)
• ISSN：1520-6041

文摘

As a further contribution to alkali-metal-mediated metalation, a method for converting C鈭扝 bonds directly to C鈭抁n bonds without the need for an additional salt metathesis step, reactions of the sodium TMP-zincate [(TMEDA)Na(渭-TMP)(渭-^tBu)Zn(^tBu)] (1) with three different electron-rich aromatic substrates, have been investigated. Under ambient-temperature conditions, N,N-diethylbenzamide, N,N-diethyl-3-methoxybenzamide, and N,N-diethyl phenyl O-carbamate were zincated ortho to the substituent group (in between both substituents in the second case) in the crystalline products [(TMEDA)Na(渭-TMP){渭-2-[1-C(O)NEt₂]C₆H₄}Zn(^tBu)] (3), [(TMEDA)Na(渭-TMP){渭-2-(1-C(O)NEt₂)(3-OMe)C₆H₃}Zn(^tBu)] (4), and [(TMEDA)Na(渭-TMP){渭-2-(1-OC(O)NEt₂)C₆H₄}Zn(^tBu)] (6). X-ray crystallography established that, in each case, the deprotonated aromatic fragment is captured by the residue of the bimetallic base, giving rise to seven-membered (NaNZnCCCO) ring structures for 3 and 4 and an eight-membered (NaNZnCCOCO) ring structure for 6. The new zincated aromatics were also characterized by solution-state ¹H and ¹³C NMR spectroscopy. Reactivity studies of 3, 4, and 6 were also performed with iodine. In each case, three molar equivalents of iodine in THF solution gave the ortho-iodo products N,N-diethyl-2-iodobenzamide (7), N,N-diethyl-2-iodo-3-methoxybenzamide (8), and N,N-diethyl-2-iodophenyl-O-carbamate (9) in quantitative, 71% and 75% yields as determined by NMR analysis, respectively.