Catalytic deprotection

Scheme 4 Catalytic deprotection of W-phenylsulfonyl amines 20 using alkyliron-ate complexes [7]...

Carrigan MD, Sarapa D, Smith RC, Wieland LC, Mohan RS (2002) A simple and efficient chemoselective method for the catalytic deprotection of acetals and ketals using bismuth triflate. J Org Chem 67 1027-1030... 

Pluth, M.D., Bergman, R.G. and Raymond, KN. (2007) Catalytic deprotection of acetals in basic solution using a self-assembled supramolecular nanozyme . Angew. Chem., Int. Ed., 119, 8741-8743. 

Ates, A., Gautier, A., Leroy B., Plancher, J.-M., Quesnel, Y, Vanherck, J.-C. and Marko, I.E. (2003) Mild and chemo-selective catalytic deprotection of ketals and acetals using cerium(IV) ammonium nitrate. Tetrahedron, 59 (45),... 

The use of a terminal 3,5-bis(benzyloxy)benzoic acid in the convergent process with internal ester connectivity permitted the catalytic deprotection (H2/Pd—C) of the benzyl groups. The resultant spherical macromolecule possessed the reactive phenolic functionality, which facilitated aqueous solubility and functionalization J87 ... 

Figure 17.22 Catalytic deprotection reaction of a photoresist system based on copolymer poly(4-hydroxystyrene-co-4-t-butyloxycarbonyloxystrene).

Ravl994 Ravindranathan, T., Chavan, S.R and Awachat, M.M., Polymer Supported Nitrobenzaldehyde Efficient, Highly Selective Catalytic Deprotection of Oxathioacetals, Tetrahedron Lett., 35 (1994) 8835-8838. 

In a second step, the acid generated catalytically deprotects the OH functionality, rendering the exposed sections base-soluble. The combination of main chain sdssion and catalytic deprotection leads to a high sensitivity of ca. 10 mJ/cm (laser focus source at 1.4 nm). Whfle no etdi rate data were communicated in the original publication, the etch rate was found to be comparable or even superior to novolak after an initial phase of film thickness loss due to t-BOC decomposition (27), a finding that is corroborated by the reported plasma stability exhibited by the related aryl sulfones, despite their high G, value see Eq. 3). 

A clever variation of the monomeric dissolution inhibitor concept (3-compo-nent system) makes use of the base-catalyzed opening of the lactone ring in cresolphthalein which becomes possible after catalytic deprotection (17b). In the t-BOC protected inhibitor, the quinomethane system cannot form, and the lacton ring is not hydrolysed. The additional acidic functionality improves the dissolution rate in the e q>osed resist (see Eq. 6). The e-beam sensitivity of a 3-component tystem based on this inhibitor in combination with a novolak matrix and a triphenylsulfonium triflate photoacid generator was reported to be 2-3 fiC/cm (17b). 

Figure 14 Basic schematic of the function of a chemically amplified resist based on photoacid-catalyzed deprotection reactions. In the simplest two-component system, exposure of a PAG produces an acid that subsequently causes the catalytic deprotection of the protected polymer resin.

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