Unusual recyclization of 2-methyl-1-phenyliso-quinolinium iodide to 1-phenyl-1,4-dihydro-3h-isochroman-3-one

Full text of DOI:10.1007/s10593-010-0516-z

Chemistry of Heterocyclic Compounds, Vol. 46, No. 3, 2010
UNUSUAL RECYCLIZATION OF 2-METHYL-1-PHENYLISO-
QUINOLINIUM IODIDE TO 1-PHENYL-1,4-DIHYDRO-
3H-ISOCHROMAN-3-ONE
V. I. Terenin1*, A. A. Volkov1, A. S. Ivanov1, and E. V. Kabanova1
Keywords: isoquinoline, isochroman-3-one, recyclization.
The formation of an isochroman-3-one was unexpectedly observed during the course of studying the
rearrangement of 1-substituted isoquinolinium salts in the presence of O-nucleophiles.
Hence refluxing 2-methyl-1-phenylisoquinolinium iodide (1) with a solution of sodium hydroxide in
alcohol and subsequent treatment with acid gave a high yield of the 1-phenyl-1,4-dihydro-3H-isochroman-3-one
(2). It was found that compound 2 is only formed after the acidification of the reaction mixture at the separation
stage.
–
1. NaOH, EtOH,
I
O

+
N
+
O
2. H
Me
Ph
Ph
2 (77%)
1
The following mechanism of formation of the isochroman-3-one 2 can be proposed. In the presence of a
nucleophile, opening of the pyridine ring of the molecule 1 occurs to form an acyclic imine (route A or B),
subsequent hydrolysis of which gives the intermediate I containing an aldehyde and a keto group. A subsequent
hydride shift from the formyl fragment to the keto group (Cannizzaro reaction) to the intermediate C occurs to
give carboxyl and alcohol groups, intramolecular esterification of which (in acidic medium) forms the
isochroman-3-one 2.
1H NMR and 13C NMR spectra were recorded on a Bruker Avance-400 spectrometer (400 and 100 MHz
respectively) using CDCl3 at a temperature of 23 and 25ºC with TMS as internal standard. Mass spectra for the
reported compounds were obtained on a Kratos MS-90 instrument with an ionization energy of 70 eV.
Monitoring of the reaction course and the purity of the products was carried out by TLC on Silufol-254
(254 nm) and Alufol plates in the systems benzene or benzene–ethyl acetate (from 5:1 to 1:1).
_______
* To whom correspondence should be addressed, e-mail: vter@org.chem.msu.ru.
1M. V. Lomonosov State University, Moscow 119992, Russia.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 454-456, March, 2010. Original
article submitted January 22, 2010.
0009-3122/10/4603-0361©2010 Springer Science+Business Media, Inc.
361

NMe
NHMe
O
O
A
B
Ph
Ph
B
–
NaOH
EtOH,
I
H2O
+
N

OH
NMe
O
NMe
A
Ph
1
Ph
Ph
~H
OH
–
–
O
O
H
O
O
OH
+
H
O
O
Ph
Ph
Ph
C
2
I
1-Phenyl-1,4-dihydro-3H-isochroman-3-one (2). A mixture of 2-methyl-1-phenylisoquinolinium
iodide (0.347 g, 1 mmol) and a solution of sodium hydroxide (10%, 4-5 ml) was refluxed in alcohol for 23 h,
cooled to room temperature, and the solvent was evaporated in vacuo. The residue was dissolved in water and
the contaminant was extracted with benzene. The aqueous phase was acidified, extracted with benzene, and the
benzene extracts were dried over CaCl2. Solvent was removed in vacuo to give the isochroman-3-one 2 (0.172 g,
77%). 1H NMR spectrum, , ppm (J, Hz): 3.63 (1H, d, J = 18.2, CH2); 3.75 (1H, d, J = 18.2, CH2); 6.39 (1H, s,
CH); 6.95 (1H, d, J = 7.5, H Ar); 7.41-7.21 (8H, m, C6H5, C6H3). 13C NMR spectrum, , ppm: 36.54, 82.10,
126.05, 127.33, 127.52, 128.80, 128.91, 128.99, 130.99, 134.63, 136.90, 170.74. Mass spectrum, m/z (Irel, %):
224 [M]+ (17), 180 (96), 179 (100), 178 (50), 165 (43), 152 (16), 119 (13), 105 (52), 89 (38), 77 (54).
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