J3enzyl-type tertiary amines were treated with n-butyllithium in ether, and the resulting metalated intermediates were treated with deuterium oxide to show the site of metalation. Benzyldimethylamine and dibenzylmethylamine afforded ortho-deuterated products, whereas 2-methyl-and 2,3-dimethylbenzyldimethylamines gave orthomethyl (side-chain) deuterated products. N,N-Dimethy1-3-phenylpropylamine was presumably metalated at the position alpha to the benzene ring. In all cases, the site of metalation was such that the amino nitrogen could coordinate with the lithium of the metalated intermediate through a fiveor six-membered ring. The formation of such a ring is thought t o be an important factor.

The first synthesis of the aromatic oxazolo[3,2‐a]pyridinium ring system has been accomplished by the cyclization of 1‐acetonyl‐ or 1‐phenacyl‐2‐pyridones. Through use of the analogous quinolones and 2‐(p‐bromophenacyl)‐1‐isoquinolone, benzologs of the new system have been prepared.

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or arylaminopyridines react directly with a! -bromoketones to afford 1-alkyl-or l-arylimidazo[l,2-a]pyridinium salts with substituents at position 2. Use of chloroacetaldoxime as the quaternizing agent yields (after hydrolysis) the imidazo-[1,2-a]pyridinium ion with no substituent at position 2. The earlier supposition that alkylation of imidazo[l,2-a]pyridines occurs in position 1 has been shown to be correct.It has been pointed out that the 1-substituted imidazo[l,2-a]pyridinium system is but one of a group of aromatic heterocyclic systems isoelectronic with the quinolizinium system.In earlier work it was shown that pyridine derivatives (I), linked in a suitable way to phenyl, could be quaternized by reaction with bromoacetone, and the quaternary salts (11) cyclized to form new tricyclic heterocyclic systems (m). Such tricyclic systems in which the linkage X is CH2-(2), -0-(3), or -S-(4) have been described. When 2-anilinopyridine (I, X = NH) i s allowed to react with bromoacetone in boiling acetone the product was not the expected 1-acetonyl salt (II, X = NH) but a dehydration product having in the infrared absorption spectrum no absorption band attributable to a carbonyl group.Since the intermediate (11, X = NH) to be expected in the quaternization reaction i s a resonance hybrid in which there is an appreciable positive charge on the NH link to phenyl, it seemed.unlikely that the facile cyclodehydration could involve an attack on the phenyl ring. Further evidence that there was no cyclization involving the phenyl group was the appearance of. infrared absorption bonds at 695, 760 and 775 ,cm-* suggesting the presence of an unsubstituted phenyl ring (5).A more plausible explanation for the cyclodehydration reaction was that the attack of the carbonyl group had occurred on the anilino nitrogen atom affording the hitherto unknown 1 -phenyl -2methylimidazo[l, 2-alpyridinium cation (ma). This theory was supported by the observation that 2-(N-methylani1ino)pyridine (I, X = N -CHs) on reaction with bromoacetone yielded the simple quaternary salt (II, X = N -CHs) rather than a cyclodehydration product. While the imidazo[l, 2-alppidine structure (Va) has been recognized as an aromatic heterocyclic system since the early investigations of Tschitschibabin (6), little attention has been devoted to the 1-alkyl o r aryl cations (VIa). These cations (VIa) have a resonancestabilized lOelectron system which formula VI could be any atom or group which can furnish two electrons to the system. The first examples of the thiazolo-(Vlb) (7,8) and oxazolo-[3,2alpyridinium (VIc) (9) cations have been described recently. To demonstrate the general nature of the reaction of a!-haloketones with salkylamino pyridines (VIII) the reactions of 2-methylamino-(R = CHs) and 2-benzylaminopyridines (R = C&&Hz) have been studied. The results are summarized in Table I. The simple 1-phenyl (IVb) and l-methylimidazo[l,2-a]pyridinium (M, = CHs, % = 3 = H) cations were prepared from the corresponding amines (VIII, Ri = CeHs o r CHs) by the use of chl...

2‐Methyl‐3‐(2‐pyridyl)quinoline (1) with a bromomethyl ketone or ethyl bromoacetate yields 6‐methyl‐12‐acylindolizino[1,2‐c]quinolinium bromides (5–9). The acyl derivatives can be deacylated in acid yielding 6‐methyl indolizino[1,2‐c]quinolinium salts (4). Benzoylation of 4 yields the 12‐benzoyl derivative (6). The deacylation product (4) has been synthesized from 2‐acetamidophenacyl bromide (10) and 2‐pyridylacetone (12).

2‐Pyridyl‐aceton (I) reagiert mit Isatin (II) zu der Säure (IIIa), die zu (IIIb) decarboxyliert und mit Selendioxid zu dem Chinolinderivat (IV) demethyliert wird.