Synthesis of Thieno [b] quinolizinium Salts

11.NEEXANE. KRXKXUER AND k'.SHORR

4380 [CONTRIBUTION FROM THE

LABORATORY O F -APPLIED

Vol. 79

ORGANIC CHEMISTRY, RESE.4RCH COUNCIL O F ISRAEL]

Synthesis of Thieno [b]quinolizinium Salts BY X. N E E ~ I A SE., ~KRAKAUER AND IT. SHORR RECEIVED JASUARY 28, 1957 3-Thenyl bromide arid pyridine-2-aldehyde reacted to form a quaternary salt, which was cyclodehydrated in boiling hydrobromic acid. The Etructure of the product, thieno[2,3-b]quinolizinium bromide, was established by desulfurizationreduction with Raney nickel to 5-ethylquinolizidine hydrobromide, which was converted into its known picrate. An analogous synthesis starting frotn 2-thenq-1chloride and pyridine-2-aldehyde yielded a small amount of product t o which the structure of thieno [3,2-b]quinolizinium bromide is asigned T h e linear thieno- and benzoquinolizinium ions show ultraviolet spectra of considerable similarity.

The synthesis of the quinolizinium ion I is of recent date.2a3 X number of benzologs of the quinoliziniuin ion have been The present study was undertaken to prepare heterocyclic ions of a new type, in which the quinolizinium ion is condensed with a thieno ring (thienologs of quinolizinium) . The synthesis of the tu70 linear thieno[ h ]quinolizinium ions (11) and (111) was attempted first, as i t was expected t h a t the two linear isomers would be accessible b y cyclodehydration of more readily available inter4

5

4

4

TABLE CLrKAVIOLET

BENZO- AXD Acridizinium perchlorate5 (VII.ClO4 -) xrr

Thieno [2,3-b]quinolizinium bromide ( I I . B r -) Am,,

IX,

m

I

ABSORPTIOX CHARACTERISTICS O F LIXEAK THIESO-QCINOLIZINIUM I O N S (IS ETHANOL)

log

24'

4.68

Xl

379.5

3,XI 4.01

399

3.93

XmnA,

mr

f11d

247

350 352

5

quinolizinium Thieno [3.2-b] bromide ( I I I . B r - )

(511)

lug