Effect of ligand structure on the zinc-catalyzed Henry reaction. Asymmetric syntheses of (-)-denopamine and (-)-arbutamine.

Halogensubstituierte aromatische Kohlenwasserstoffe sowie halogenierte Aniline, Dimethylaniline, Phenole, Anisole, Naphthole, Benzoesauren, Pyridine und Chinoline lassen sich bei Zimmertemperatur mit Raney-Nickel in Gegenwart aquivalenter Menge an Basen in guter Ausbeute und stets reproduzierbar hydrierend enthalogenieren. Bei gleichwertig substituierten Dihalogenverbindungen konnen die Halogenatome in Abhangigkeit von der Menge an vorgelegter Base schrittweise entfernt werden.

Die hydrierende Dehalogenierung aromatischer Halogenverbindungen mit Raney‐Nickel und Alkali

Eine Reihe von Hydroxybenzylalkoholen wurde durch Reaktion von Phenolen mit Formaldehyd bzw. durch NaBH4-Reduktion der entsprechenden Hydroxybenzaldehyde dargestellt. Die Oxydation mit K3Fe(CN)6 fuhrte in den meisten Fallen unter Abspaltung von Hydroxymethylgruppen als Formaldehyd zu polymeren Kupplungsprodukten, im Falle von 2,6-disubstituierten p-Hydroxybenzylalkoholen zu linearen Polyphenylenathern. p-Hydroxybenzylalkohole mit elektronenanziehenden Substituenten ergaben die entsprechenden p-Hydroxybenzaldehyde. Die Oxydation mit O2 inDMSO in Gegenwart von Cu(I)Cl fuhrte im Falle der o-Derivate meist zu oligomeren Produkten, die p-Derivate hingegen ergaben neben Oligomeren und p-Chinonen zumeist die entsprechenden Benzaldehyde als Hauptprodukte.

Darstellung und Oxydation von Hydroxybenzylalkoholen

Farbe und Konstitution, VIII1). Zum Problem der Solvatochromie bei Merocyaninen

Es wird die Darstellung von Oxymethylphenolen, als “Phenolalkohole” bekannt, durch hydrierende Dehalogenierung entsprechender kernhalogenierter Oxymethylphenole beschrieben. Die Dimethylenathergruppe in 1.1′-Dioxy-dibenzylather bleibt bei dem beschriebenen Hydrierverfahren mindestens in einem Ausmas von 60–80% ungespalten.

Zur Darstellung von Oxymethylphenolen durch hydrierende Dehalogenierung kernhalogenierter Oxymethylphenole

The preparation of I-hydroxy-2 : 6-bis-(2-hydroxybenzyl)benzene by dehalogenation of the corresponding trichloro compound was described in Part X of this series (Finn, Lewis & Megson, 1950). The removal of the chlorine was effected by treatment of the boiling amyl alcohol solution of the compound with sodium. The yield was poor and amounted to only 5% of theory.



It has now been found that the dehalogenation can be achieved more satisfactorily by treatment of a solution of the diphenylmethane derivative in aqueous sodium hydroxide with Raney nickel-aluminium alloy. A yield of about 50% of theory is obtained.



2 : 2′-Dihydroxydiphenylmethane may be obtained from 2 : 2′-dihydroxy-5 : 5′-dichloro-diphenylmethane by the same means and the method has been used to prepare 2 : 2′-dihydroxy-3 : 5-dimethyldiphenylmethane, 2 : 2′-dihydroxy-3 : 3′ : 5 : 5′-tetramethyldiphenylmethane, and I-hydroxy-3 : 5-dimethyl-2 : 6-bis-(2-hydroxybenzyl)benzene.

Formaldehyde condensations with phenol and its homologues. XII. The dehalogenation of halogenated diphenylmethanes having halogen substituents in the nucleus

A major obstacle in the chemistry of phenolic resins is the difficulty in preparing some of the simple phenolic alcohols, owing to their reactivity and the formation of isomers which are not readily separated. The use of halogenated phenols, in which one or more of the free reactive nuclear positions are blocked by halogen atoms, generally avoids both further reaction and the formation of isomers. If a simple means existed of removing the halogen from alcohols prepared from such halogenated phenols, under mild conditions which would not cause further reaction of the product, then a method would exist for the preparation of many phenolic alcohols which cannot be prepared by the direct reaction of formaldehyde and the appropriate phenol. It has now been shown that this process can be accomplished by the use of Raney alloy in the presence of aqueous sodium hydroxide. A new alcohol of phenol (2:6-dihydroxymethylphenol) has been prepared by this means.

Formaldehyde condensations with phenol and its homologues. XIV The dehalogenation of phenolic alcohols having halogen substituents in the nucleus

The structure of the monoalcohol of 3 : 5-dimethylphenol, first made by von Auwers and believed to be a para-substituted derivative, has now been confirmed. The synthesis of a new dialcohol, which has been characterized as an ortho-ortho compound, is described. The effect of reaction conditions on the position of methylol substitution is discussed. It has been shown that during characterization of the monoalcohol, by pyrolysis with lime, methyl migration may occur.

Formaldehyde condensations with phenol and its homologues. V. The methylol compounds of 3 : 5‐dimethylphenol

In Part V of this series, it was shown that the reaction of formaldehyde with 3:5-dimethylphenol could result in the formation of either the p-monoalcohol or the 0-0′-dialcohol, according to the reaction conditions.



The 0-monoalcohol (2-hydroxymethyl-3:5-dimethylphenol) has now been prepared from 2-dimethylaminomethyl-3:5-dimethylphenol by conversion with acetic anhydride to 1-acetoxy-2-acetoxy-methyl-3:5-dimethylbenzene, followed by reduction of the latter with lithium aluminium hydride. This process may be expected to provide a general method for the preparation of phenolic alcohols from the parent phenols.



The structure of the 0-alcohol has been confirmed by reduction of the corresponding aldehyde with lithium aluminium hydride.

Formaldehyde condensations with phenol and its homologues. XI. The preparation of 2‐hydroxymethyl‐3:5‐dimethylphenol by a new general method

In earlier papers of this series it has been shown that the action of formaldehyde on 3 : 5-xylenol in the presence of sodium ethoxide catalyst results in the formation of an ortho-ortho-dialcohol. Attempts to prepare as ortho-monoalcohol by modification of the reaction conditions foiled. A consideration of the behaviour of other substituted phenols appears to lead to a generalization that when both meta positions and sometimes when the para position of phenols, relative to the phenolic hydroxyl group, are occupied by substituents, the introduction of a methylol group into one ortho position results in an enhanced reactivity of the other. Such an enhanced reactivity of one ortho position would explain why dialcohols are readily formed, but that the presumably intermediate mono-alcohol cannot be isolated.



Attempts to prepare some trinuclear substituted compounds by condensation of di-ortho-substituted phenols with various intermediates failed. The explanation of this failure is probably due to a decreased reactivity of the para position in these di-ortho-substituted phenols.

Formaldehyde condensations with phenol and its homologues. XIII.The relative reactivity of the ortho AND para Positions in the formation of alcohols of substituted phenols

S. R. Finn

Papers

Formaldehyde condensations with phenol and its homologues. XII. The dehalogenation of halogenated diphenylmethanes having halogen substituents in the nucleus

Formaldehyde condensations with phenol and its homologues. XIV The dehalogenation of phenolic alcohols having halogen substituents in the nucleus

Formaldehyde condensations with phenol and its homologues. V. The methylol compounds of 3 : 5‐dimethylphenol

Formaldehyde condensations with phenol and its homologues. XI. The preparation of 2‐hydroxymethyl‐3:5‐dimethylphenol by a new general method

Formaldehyde condensations with phenol and its homologues. XIII.The relative reactivity of the ortho AND para Positions in the formation of alcohols of substituted phenols