TY - JOUR
T1 - Gas-phase chemistry of acylium ions
T2 - Seven-to-five ring contraction of 1,3-dioxepane and 1,3-dioxep-5-ene
AU - Moraes, Luiz Alberto B.
AU - Kotiaho, Tapio
AU - Eberlin, Marcos N.
N1 - Project code: K9SU00137
PY - 1999
Y1 - 1999
N2 - As shown by pentaquadrupole triple‐stage mass spectrometric and 18O‐labeling experiments, two seven‐membered cyclic acetals, 1,3‐dioxepane and 1,3‐dioxep‐5‐ene, fail to react by transacetalization with the gaseous acylium ions CH3C+=O and (CH3)2NC+=O. Instead, a novel and less exothermic but more kinetically favored reaction, seven‐to‐five ring contraction, occurs predominantly, and to great extents with the most reactive acylium ion, (CH3)2NC+=O. 1,3‐Dioxepane yields O‐acylated tetrahydrofurans; 1,3‐dioxep‐5‐ene yields O‐acylated 2,5‐dihydrofurans.
AB - As shown by pentaquadrupole triple‐stage mass spectrometric and 18O‐labeling experiments, two seven‐membered cyclic acetals, 1,3‐dioxepane and 1,3‐dioxep‐5‐ene, fail to react by transacetalization with the gaseous acylium ions CH3C+=O and (CH3)2NC+=O. Instead, a novel and less exothermic but more kinetically favored reaction, seven‐to‐five ring contraction, occurs predominantly, and to great extents with the most reactive acylium ion, (CH3)2NC+=O. 1,3‐Dioxepane yields O‐acylated tetrahydrofurans; 1,3‐dioxep‐5‐ene yields O‐acylated 2,5‐dihydrofurans.
U2 - 10.1002/(SICI)1096-9888(199906)34:6<670::AID-JMS819>3.0.CO;2-H
DO - 10.1002/(SICI)1096-9888(199906)34:6<670::AID-JMS819>3.0.CO;2-H
M3 - Article
SN - 1076-5174
VL - 34
SP - 670
EP - 676
JO - Journal of Mass Spectrometry
JF - Journal of Mass Spectrometry
IS - 6
ER -