{'fraction_non_alphanumeric': 0.03935483870967742, 'fraction_numerical': 0.01935483870967742, 'mean_word_length': 5.516806722689076, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
MANGANESE DIOXIDE SUPPORTED ONTO HZSM-5 ZEOLITE, A VERSATILE REAGENT FOR THE AROMATIZATION OF HANTZSCH 1,4-DIHYDROPYRIDINES

INTRODUCTION Hantzsch 1,4-dihydropyridines (1,4-DHPs) have attracted considerable attention as calcium channel blockers for the treatment cardiavascular diseases (1). During the redox processes (2) and in the course of drug metabolism (1b) 1,4-DHP systems are oxidatively transformed into the corresponding pyridine derivatives. Oxidation of Hantzsch pyridine usually yields the corresponding pyridine derivatives, but expulsion of the substituent in the 4 position has been for some oxidant is observed (3). A plethora of reagents has been used for this oxidation. Aromatization of 1,4 DHP has been achieved using various oxidants such as nitric acid (4), CAN (5), ferric or cupric nitrates (6), nitric oxide (7), PCC (8), clay supported cupric nitrate accomplished under ultrasound promotion (8), TEMDO BF4 (9). However many of the reported methods either suffer from the use of strong oxidant, require serve conditions or need excess of oxidant. Manganese dioxide (10) and manganese triacetate (11) have also been used for Hantzsch 1,4-DHP oxidation. However these methods also suffer from the disadvantage of prolonged reaction time, drastic reaction conditions and tedious work up procedures. In view of the above limitations and since manganese compounds are inexpensive, available and relatively benign oxidant, we decided to develop a practical and general approach for this oxidative conversion using a mild oxidant,