Syntheses, transformations and applications of aminonaphthol derivatives prepared via modified Mannich reactions

Szatmári, István and Fülöp, Ferenc (2013) Syntheses, transformations and applications of aminonaphthol derivatives prepared via modified Mannich reactions. TETRAHEDRON, 69. pp. 1255-1278. ISSN 0040-4020

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Abstract

A special alteration is the three-component modi fi ed Mannich reaction (mMR), in which formaldehyde is replaced by an aromatic aldehyde, the secondary amine by ammonia, and the C e H acid by an electron-rich aromatic compound such as 1- or 2-naphthol, quinolinol or isoquinolinol. Based on this, it can be interpreted as a formal Mannich reaction. Starting from ammonia, benzaldehyde, and 2-naphthol in this mMR, 100 years ago, Mario Betti reported the straightforward synthesis of 1,3-diphenylnaphthoxazine in methanol. Acidic hydrolysis of the ring compound produced led to 1-aminobenzyl-2-naphthol. The aminonaphthol product became known in the literature as a Betti base, and the protocol as the Betti reaction. 3 e 5 This reaction has subsequently been extended by using different N sources, the order and character of which (ammonia, amine or amide) greatly determine the reaction conditions and the method of isolation of the Mannich product. 6 On the other hand, the use of non-racemic amines has opened up a new area of ap- plication of enantiopure aminonaphthols as chiral catalysts in enantioselective transformations.

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