Deprotection chemistry

Scheme 11. Octa S-benzylporphyrazines and deprotection chemistry. [Adapted from (3), (23-24).]...

In this paper, we report an alternative approach to the design of deep UV resist systems combining the desired properties, which involves copolymerization of methacrylic ester with styrenic comonomer and the use of the acid-catalyzed deprotection chemistry. 

Ar"-2-Adamantyloxymethyl protectionP is similar to AT -Bom in both its protection and deprotection chemistry (except that it is hydrogenolysis resistant), but peptides protected with this variant may have solubility advantages. 

The parent spacer, 4-hydroxybutanoic acid, spontaneously undergoes loss of water under acidic or basic conditions to give 4-butyrolactone. To prevent cyclization when the spacer is coupled to methoprene, both the hydroxyl and carboxyl functions had to be protected and selectively deprotected. The methods used are summarized in Figure 2. The protection/deprotection chemistry described was originally developed for use in the field of peptide synthesis. 

The deprotection chemistry has been incorporated into the acid generator structure itself [177]. Phenolic hydroxyl groups pendant from triphenylsulfonium salts were protected with tBOC (Fig. 43). This dissolution inhibiting PAG mixed with PHOST becomes base soluble through photochemically-induced acid-catalyzed deprotection and thus the exposed area dissolves rapidly in aqueous base, which was named SUCCESS and promoted by BASF. A similar approach has been later reported on o-nitrobenzyl sulfonate acid generators, in which a tert-butyl ester was attached to the benzene ring for acid-generation and acid-catalyzed deprotection on one molecule (Fig. 43) [178]. 

LER and resist outgassing during exposure are major issues in bilayer lithography [438, 439]. Si species generated from a bilayer resist during exposure could badly contaminate lenses. Thus, formation of gaseous products must be minimized by proper selection of deprotection chemistry and resist components. 

McBride LJ, Kierzek R, Beaucage SL, Caruthers, MH. Amidine protecting groups in oligonucleotide synthesis. J Am Chem Soc 108 2040-2048, 1986. Vinayak R, Anderson P, McColum C, Hampel A. Chemical synthesis of RNA using fast oligonucleotide deprotection chemistry. Nucleic Acids Res 20 1265-1269, 1992. 

Fig. 46. Deprotection chemistry utilized to produce polymethacrylic acid or its salts.

The direct synthesis of functional, self-assembling copolymers in aqueous media under mild conditions without protection/deprotection chemistry steps, however, remains a current challenge that focuses research efforts on developing stimuli-responsive delivery systems such as micelles... 

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