Cyclodextrins Reimer-Tiemann reaction

Divakar, S., Maheswaran, M. M., Narayan, M. S. Reimer-Tiemann reactions of guaiacol and catechol in the presence of P-cyclodextrin. Indian J. Chem., Sect. B1992, 31B, 543-546. 

Ravichandran, R. P-Cyclodextrin mediated regioselective photo-Reimer-Tiemann reaction of phenols. J. Mol. Catal. A Chemical 1998,130, L205-L207. 

The photo-Reimer-Tiemann reaction of phenols with chloroform in the presence of 3-cyclodextrin has been reported to produce 4-hydroxy-benzaldehydes with high selectivity. ... 

Since the Reimer-Tiemann reaction always yields a mixture of ortho- and para-substituted phenols whenever the two positions are unsubstituted (and sometimes even when the positions are substituted, see carboxy-substituted phenols), it is not surprising that attempts have been made to increase the regioselectivity. Earlier attempts (for details, see reviews) emphasized the nature of the cation, the solvent, or used phase-transfer catalysis. Recent studies have concentrated on the use of cyclodextrins as base-stable host compounds, permitting exclusive para substitution. Attaching the cyclodextrins to a solid support has also been attempted, a natural step in view of the high cost of the cyclodextrins and the need for cheap product i.e. p-hydroxybenzaldehyde). p-Hydroxybenzaldehyde has been prepared in 59-65% yield using P-cyclodextrin that has been immobilized with epichlorohydrin. TTie catalyst is easily recovered and can be reused without appreciable loss of activity. 

As is the case with the normal reaction, the abnormal reaction can also be influenced by the use of 3-cyclodextrin to give higher selectivity for the para position. Australian chemists have carried out a careful product analysis of the normal, abnormal and ring-expansion products resulting from the Reimer-Tiemann reaction with a series of 4-alkylguaiacols. ... 

In an interesting modification of the Reimer-Tiemann reaction the dropwise addition of chloroform to a mixture of phenol and a-cyclodextrin in 10% aqueous sodium hydroxide at OO C and reaction over 10 hours afforded 4-hydroxybenzaldehyde in 46% yield (ref. 10). Both these methods are shown below... 

In order to develop catalytic effects of cyclodextrins for bimolecular reactions, it needs to include two guest molecules simultaneously in a cyclodextrin (CD) cavity. Several examples of cyclodextrin-catalyzed bimolecular reactions have been reported. Rideout and Breslow have found that Diels-Alder reactions of cyclo-pentadiene with butenone, cyclopentadiene with acrylonitrile, and anthracene-9-carbinol with N-ethylmaleimide in water are markedly accelerated by 3-cyclodextrin (3-CD) (1). Komiyama and Hirai have reported site-selective Reimer-Tiemann reactions of phenols in cyclodextrin solutions (2). In most of these reactions, however, each substrate molecule is relatively small so that a 3-CD cavity may include simultaneously an additional reactant molecules. We found previously that the fluorescence quenching of pyrene and naphthalene by trimethylamine (TMA) or dimethylamine (DMA) in water is catalyzed by g-CD (3) Since the pyrene molecule is too large to be incorporated completely in the 3-CD cavity, it has been assumed that pyrene binds to a rim of the CD cavity to form a pyrene-capped CD complex and a remain-... 

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