Mass spectrometric determination of the configuration of the 4‐substituted 1,2‐dimethyl‐4‐hydroxydecahydroquinolines

Abstract

The mass spectra of a number of the epimeric 1,2-dimethyl-4-alkyl-4-hydroxydecahydroquinolines (alkyl: C z C H , CH=CH,, C,H, and COCH,) have been studied. The configuration at C-2 and C-4 in these molecules is proposed on the basis of the data obtained. Some aspects of the fragmentation pathways under electron-impact are discussed.

Electron ionization mass spectra of phosphorus‐containing heterocycles. II. 1,2,3,4,4a,5,6,7,8,8a‐decahydro‐1,3,2‐benzodiazaphosphinine 2‐oxides

“…(6–9%) and [M–C 7 H 9 ] + (5–7%) as the most abundant ions. Compounds 3 and 4 gave [M–C 6 H 11 ] + (8–11%), [M–C 7 H 11 ] + (6–7%) (this is comparable with the situation for decahydroquinolines,8–10 some other heterocyclic compounds studied earlier,17 and 1,4,4a,5,6,7,8,8a‐2 H ‐3,1,2‐benzoxazaphosphinine 2‐oxides1 when R 1 = CH 3 and R 2 = Ph), [M–NH 3 ] + . (7–13%), and [M–CH 3 NH] + (5–6%) as the most abundant ions.…”

“…The respective ions are stabilized by conjugation (Scheme ), which in this case also makes formation of [M–C 4 H 9 ] + favored although it was of minor importance in the corresponding 3,1,2‐O,N,P derivatives 1. This type of fragmentation is common for bicyclic N heterocycles8–12 and it has also been observed for some perhydro‐1,3‐oxazine derivatives 13, 14…”

Stereospecific Ion—molecule Reactions in the Trans-Decahydro-4-Hydroxyquinoline Series upon Chemical Ionization

“…It is worth mentioning that protonation of the hydroxyl group proceeds more readily than that of the N atom in many cases, although the proton affinity of the amine nitrogen atom is higher than that of the hydroxyl group. Only in the case of the N-unsubstituted alcohols (8,9) is the opposite picture observed. This means that steric hindrance can prevent the protonation of the N atom.…”

“…Their structure and stereochemistry has been proved earlier. 9,10 Owing to their high volatility, the samples were introduced into the ion source of the mass spectrometer through the gas chromatographic inlet.…”

“…The isobutane CI mass spectra of all the studied alcohols (1-9) show mainly two intense peaks due to the protonated molecule [ (1)(2)(3)(4)(5)(6)(7)(8)(9) are given in Table 1. It should be underlined once more that, even though the proton affinities (PA) of hydroxyl and amino groups are different (for example, PA of aliphatic alcohols is~810 kJ mol -1 and PA of aliphatic amines is8 80 kJ mol -1 ), protonation of the N-heterocyclic alcohols (1-9) proceeds at both functional groups and, hence, this process is kinetically controlled.…”