The measurement of the pKa of racemic tetramethoxyresorcin[4]arenes explains the failure to obtain good yields in attempted Mannich reactions of these substrates under classical reaction conditions. The failure is related to the lack of adequate concentrations of the iminium ions that results from the reduced acid strength of tetraalkoxyresorcin[4]arenes compared with that of the parent octahydroxyresorcin[4]arenes. However, the preparation of a series of Mannich bases derived from racemic tetraalkoxyresorcin[4]arenes was accomplished under microwave‐assisted aprotic reaction conditions and the use of preformed iminium ion intermediates. When the reactions were carried out with the use of chiral bis(aminol) ethers, mixtures of diastereomers were obtained that could be separated by flash chromatography. The absolute configurations of the enantiomerically pure tetrabenzoxazine derivatives were established in some cases by X‐ray crystallographic analysis and by a comparison of the nuclear magnetic resonance spectroscopic data. The alkylation of racemic tetramethoxyresorcin[4]arenes was achieved with the use of an excess of 2‐bromo‐N‐[(R)‐(+)‐(α‐methylbenzyl)]acetamide in acetonitrile containing potassium carbonate. Enantioselective ligand‐assisted reactions of aromatic aldehydes are also reported with the use of dialkylzinc reagents both in the absence and in the presence of terminal alkynes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Novel racemic tetraalkoxyresorcinarene derivatives can be prepared in good yields by boron trifluoride diethyl etherate-catalysed reactions of 1,1-dimethoxyalkanes with resorcinol monoalkyl ethers.

The desymmetrisation of resorcinol to give 3-alkoxyresorcinol derivatives can be achieved in excellent yields either from resorcinol monobenzoate and alcohols using Mitsunobu reactions followed by hydrolysis using a strong base or by using 3-iodophenylbenzyl ether as a resorcinol monobenzyl ether equivalent in reactions with alcohols catalysed by copper(I)-9,10-phenanthroline followed by ammonium formate-palladium catalysed hydrogenolysis.

The measurement of the pKa of a racemic tetramethoxyresorcin[4]arene explains the failure to obtain good yields in attempted Mannich reactions of tetraalkoxyresorcin[4]arenes under classical reaction conditions. The failure is related to the lack of adequate concentrations of iminium ions that results from the reduced acid strength of tetraalkoxyresorcin[4]arenes as compared to parent octahydroxyresorcin[4]arenes. However, the preparation of a series of Mannich bases derived from racemic tetraalkoxyresorcin[4]arenes was accomplished using aprotic reaction conditions, including microwave assisted reactions, and using pre-formed iminium ion intermediates. In the case of reactions using chiral bis(aminol)ethers, the reactions gave mixtures of diastereoisomers that were separated by flash chromatography. The absolute configurations of the enantiomerically pure tetrabenzoxazine derivatives were established as (P,R,S) or (M,S,R), in some cases by Xray crystallographic analysis, and by a comparison of nuclear magnetic resonance spectroscopic data. The alkylation of racemic tetramethoxyresorcin[4]arenes was achieved in reactions using an excess of N-(R)-(+)-α-methylbenzyl-2-bromoacetamide in acetonitrile containing potassium carbonate. Enantioselective ligand-assisted reactions of aromatic aldehydes are reported using dialkylzinc reagents both in the absence and presence of terminal alkynes.

Ethers. -The synthesis of monoethers (VI) and (X) derived from resorcinol is achieved by etherification of 3-alkoxyiodobenzene (III) or resorcinol mono benzoate (VII) followed by deprotection. -(BOXHALL, J. Y.; PAGE, P. C. B.; CHAN, Y.; HAYMAN, C. M.; HEANEY*, H.; MCGRATH, M. J.; Synlett 2003, 7, 997-1001; Dep. Chem., Univ. Technol., Loughborough, Leicestershire LE11 3TU, UK; Eng.) -Mais 41-089