Fragmentation process amines

Scheme 55, Eq. 55a) [119]. A plausible mechanism is depicted in Scheme 55 and involves radical addition of the 2-tetrahydrofuryl radical to the aldehyde followed by a rapid reaction of the alkoxyl radical with Et3B. Triethylborane has a crucial role since by reacting with the alkoxyl radical it favors the formation of the condensation product relative to the -fragmentation process (back reaction). A similar reaction with tertiary amines, amides and urea is also possible (Eq. 55b) [120]. 

Duffield, A.M. Budzikiewicz, H. Williams, D.H. Djerassi, C. Mass Spectrometry in Structural and Stereochemical Problems. LXIV. A Study of the Fragmentation Processes of Some Cyclic Amines. J. Am. Chem. Soc. 1965, 87, 810-816. 

Usually, PET processes are preferred to other fragmentation processes in HMPA, but only dialkylthiocarbamates give satisfactory yields of R -H. Again a very good parallel can be drawn between the PET reaction of carbonic acid derivatives and their reduction by dissolving metals in primary amines or HMPA. ... 

This pattern is very different from that of proteonated PC species (see last section). The resultant [M-i-H-141]+ ion, rather than a protonated PE species at m/z 142 (equivalent to the m/z 184 ion resultant from proteonated PC species), indicates that the phosphoethanolamine is less competitive for a proton, but easy to lose a proton from the primary amine. Extensive mechanistic studies have demonstrated that the fragmentation process leading to the generation of [M-fH-141]+ ion also involves the participation of the a-hydrogen atoms of the FA substituent, mainly that at the sn-2 position [1,4,9]. Figure 7.3a shows a representative product-ion ESI-MS spectrum of protonated 16 0-22 6 diacyl PE (dPE) after CID. 

Secondary and tertiary amines also undergo fragmentation processes as described earlier. The most important fragmentation is p-cleavage. In the mass spectrum of diethylamine (Fig. 4.56),... 

The secondary process of amine fragmentation (1,3-sigmatropic shift) may be used as an example of a process initiated by the charge center (Scheme 5.18). 

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