Ringschlußreaktionen von Acetylenketonen mit zweifach CH‐aciden Verbindungen zu Phenolen

Abstract

Acetylenketone 1 und CH-acide Verbindungen von der Art des Dibenzylketons reagieren in Gegenwart von K-tert.-butglat zu substituierten Phenolen 4. 2.3.5.6-Tetrasubstituierte Phenole werden mit CrO,/Eisessig je nach Substitution zu Benzochinonen l l a -f bzw. zu Fluorenchinonen 9 und 10 oxydiert. In HBr/Eisessig reagieren Phenole vom Typ 4a bzw. 4f zu Fluorenolen, wic: 12, bzw. zu Phthalanen, wie 13. Cyclisation Reactions of Alkynones with Double CH-Acid Compounds to PhenolsAlkynones 1 and CH-acid compounds like dibenzyl ketone react to substituted phenols 4 in the presence of K-tert-butylate. Depending on the substituents, 2,3,5,6-tetrasubstituted phenols are oxidized by Cr03/acetic acid to benzoquinones l l a -f or fluorene quinones 9 and 10. In a solution of HBr/acetic acid phenols of the type of 4a or 4f form fluorenols like 12 or phthalanes like 13. Darstellung von AcetylenketonenAcetylen-Grignard-Verbindungen reagieren mit Aldehyden zu sekundaren Alkinolen 2). Diese werden durch Cr03-Oxydation in Acetylenketone uberfuhrt. Nach dieser Methode lassen sich die Acetylenketone l a -d in guten Ausbeuten darstellen.

The synthesis of 2,3,5-trisubstituted phenols

“…3a-d Synthetic strategies used for the preparation of 2,3,5-polysubstituted phenols include the following multistep sequences: (i) from pyrylium salts and nitromethane 4 and (ii) by basecatalyzed reactions of pre-formed ethynyl ketones with benzyl ketones. 5 Our recent study of [3+3] annulation reactions of 1-(benzotriazol-1-yl)propan-2-one with chalcones 6 gave an access to 3,5-diarylphenols advantageous as compared to the previously reported aromatization of cyclohexenones 7a,b and Michael addition/aldol condensation of 1-(2-oxopropyl)pyridiniums salts with chalcones. 8 No general method has previously been described for the preparation of meta-acylphenols, few of which are known.…”

Indeno-Annulation of o-Formyl-Ynones, o-Bis-Ynones, and p-Bis-o-Formyl-Ynones with Dimethyl Acetone-1,3-Dicarboxylate: One Flask Cascade Synthesis of Functionally Endowed 9-Fluorenols and Indeno[1,2-b]fluorenols

“…As part of our ongoing activity toward rapidly accessing complex polycyclic frameworks from ynones, we were drawn to a known reaction between aryl ynones A (R 1 = H) and dimethylacetone-1,3-dicarboxylate (DMAD), two functionally well-endowed table top substrates, each harboring three complementary reactive C-sites, Figure . This reaction leads to an interesting but unexceptional formation of a penta-substituted phenol derivative D through intermediacy of B and C involving sequential Michael addition–aldol cyclization–aromatization sequence in one-pot reaction, as shown in Figure .…”

A Convenient One-Pot Method for the Construction of Tetrasubstituted Phenols through a Michael Addition−Aldol Cyclization Sequence

“…This reaction can be explained by a sequence of steps involving Michael addition followed by aldol cyclization through the enolate intermediates (Scheme ). The analogous reaction with alkynones has been described 1 …”