Phenol, condensation with chloral

Historically, one of the first examples of enantioselective arene (i.e., phenols) decoration was reported by an Italian team (Casiraghi and coworkers) [4] that documented on the efficiency of (-)-menthoxy(ethyl)aluminum chloride 3 as a chiral stoichiometric LA, in promoting the condensation of a range of phenols 1 with chloral 2. Enantiomeric excesses up to 80% were obtained (Scheme 5.1a). Shortly after, the first catalytic variant was realized by Erker and coworkers that described the stereoselective addition (ee up to 84%) of 1-hydroxynaphthalene (5a) to methyl or ethylpyruvate (6a,b) in the presence of chiral zircono-cene 7 (Scheme 5.1b) [5]. 

Of numerous chloral condensations with aromatic hydrocarbons the most interesting for the synthesis of condensation monomers are the reactions with benzene [3], toluene [4], acenaphthene [5], phenol [6], anisol [7], acetanilide [8] and halobenzenes like chlorobenzene [9] and fluorobenzene [10]. In general terms, these reactions proceed according to Scheme 2.2 and give the desired 1,1,1-trichloro-... 

Other aldehydes used for the synthesis of phenolic polycondensates include butyraldehyde, furfural or chloral. Efficient AO, e.g. polycondensate 129, were prepared with sulfur containing aldehydes [161]. Linear polycondensates of phenols and aldehydes were tested as AO in mineral oils, PE, PP, poly (ethylene-co-propylene), PS, PA and/or diene based rubbers [159, 162]. Cyclic phenolic condensates, calixarenes (130) posses interesting properties. Calixarenes were synthesized from 4-acyl-, 4-methyl-, 4-tm-butyl- or 4-phenylphenol in alkaline catalysed processes. Cycles containing 4 to 7 phenolic units were formed and tested as AO in PE or PP [163,164], Nickel(II) salt of 130 (R = lerf-butyl, n = 1)... 

BPC was carried out by condensing phenol with chloral to produce 1,1,1 -trichloro-2,2-bis(4-hydroxyphenyl) ethane (3) followed by a dehydrohalogenation to give the corresponding dehydrohalogenated compound BPC (4) (Fig. 8). ° ... 

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