4, 5-Diphenylpyrimidine (DPP) was obtained on heating deoxybenzoin (DB) with formamide and POCl
3.
1) Several deoxybenzoins to generalize this preparative method, and following results were obtained. None from 4, 4'-di (CH
3O) DB (I), 3, 4-3', 4'-bis (OCH
2O)-DB (II), and 3'-(NH
2)-4-(CH
3O) DB (XIXc) ; 4-(4-CH
3O)-5-(4-NO
2) DPP (V) from 4-(CH
3O)-4'-(NO
2) DB (III), 4-(4-NH
2)-5-(4-CH
3O) DPP (VI) from 4'-(CH
3O)-4-(NO
2) DB (IV), 5-(4-NH
2) DPP (XI
a) from 4'-(NO
2) DB (Xa) ; 5-(3-NO
2) DPP (XIb) from 3'-(NO
2) DB (Xb) ; 4-(4-CH
3O)-5-(3-NH
2) DPP (XIc) from 3'-(NO
2)-4-(CH
3O) DB (Xc) ; 6, 8-dimethoxy-3-phenylisoquinoline (XIII) from 3', 5'-di(CH
3O) DB (XII) ; 5-(3, 4-di (CH
3O) DPP (XVI) with some 6, 7-dimethoxy-3-phenylisoquinoline (XV) from 3', 4'-di(CH
3O) DB (XIV) ; 5-(3-CH
3O)- DPP (XIII), from 3'-(CH
3O) DB (XVII) ; 5-(3-NH
2) DPP (XXa) from 3'-(NH
2) DB (XIXa) ; 5-(3-HO) DPP (XXb) from 3'-(HO) DB (XIXb) ; 4-(4-CH
3O)-5-(3-HO) DPP (XXd) from 3'-(HO)-4-(CH
3O) DB (XIXd). From these results, the following will be concluded : (1) To form isoquinolines, at least two +R groups (e.g. CH
3O) must be substituted in the meta and other positions of benzyl in DB. When there is only one substituent at the meta-position of the benzyl group, even though more effective as NH
2 or OH, isoquinoline ring-closure does not take place but the corresponding pyrimidines are obtained. (2) NO
2 substituent is often reduced to NH
2 in this procedure. (3) The presence of +R substituent at the para-position of the benzoyl group of DB deactivates vates this reaction and -R substituent accelerates it.
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