Organic Lab Reactions 174

Organic Lab Reactions 174 - STANNIC CHLORIDE ON THE FREE...

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STANNIC CHLORIDE ON THE FREE ACID 169 Other Methods The extent of consideration given to the methods of cyclization dis- cussed below is not intended to be an indication of the relative merits of the methods but is-necessarily limited by the available experimental data. Stannic Chloride pn the Free Acid. Ring closure by heating the free acid with stannic chloride at 100-120° has been shown to be successful on several types of acids. 38 - "• "• 66 ' 80 - 18B - a19 These and some other acids which have been cyclized by this method may be found in Table XI. In four instances (items 3, 7, 14, 17) stannic chloride treatment gave better results than sulfuric acid. Eleven of the acids in Table XI (items 3, 5, 8, 9, 10, 12, 13, 14, 16, 17, 18) have been cyclized also by the Friedel-Crafts method on the acid chloride. With seven acids (3, 6, 8, 9, 12, 14, 17) the yields were better, while with four (5, 10, 16, 18) they were lower, than with stannic chloride. Except for one (18) of these latter acids, however, there seems to be some question as to whether the
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