Electrospray Ionization (ESI) Fragmentations and Dimethyldioxirane Reactivities of Three Diverse Lactams Having Full, Half, and Zero Resonance Energies

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• 作者：Kathleen M. Morgan ; David J. Ashline ; Jessica P. Morgan ; Arthur Greenberg
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：January 17, 2014
• 年：2014
• 卷：79
• 期：2
• 页码：517-528
• 全文大小：764K
• ISSN：1520-6904

文摘

Three lactams having, respectively, 20, 10, and 0 kcal/mol of resonance energy have been subjected to electrospray ionization mass spectrometry (ESI/MS) as well as to attempted reaction with dimethyldioxirane (DMDO). The ESI/MS for all three lactams are consistent with fragmentation from the N-protonated, rather than the O-protonated tautomer. Each exhibits a unique fragmentation pathway. DFT calculations are employed to provide insights concerning these pathways. N-Ethyl-2-pyrrolidinone and 1-azabicyclo[3.3.1]nonan-2-one, the full- and half-resonance lactams, are unreactive with DMDO. The 鈥淜irby lactam鈥?(3,5,7-trimethyl-1-azaadamantan-2-one) has zero resonance energy and reacts rapidly with DMDO to generate a mixture of reaction products. The structure assigned to one of these is the 2,2-dihydroxy-N-oxide, thought to be stabilized by intramolecular hydrogen bonding and buttressing by the methyl substituents. A reasonable pathway to this derivative might involve formation of an extremely labile N-oxide, in a purely formal sense, an example of the hitherto-unknown amide N-oxides, followed by hydration with traces of moisture.