Trityl alcohol

Trityl alcohol, t416 Triptamine, al70 Tyramine, al73 Umbelliferone, hill... 

Problem 11.42 Explain the following observations, (a) A yellow color is obtained when Ph,COH (trityl alcohol) is reacted with concentrated H2SO4, or when PhjCCI is treated with AICI,. On adding HjO, the color disappears and a white solid is formed, (b) Ph,CCl is prepared by the Friedel-Crafts reaction of benzene and CCI4. It does not react with more benzene to form PhjC. (c) A deep-red solution appears when Ph,CH is added to a solution of NaNH in liquid NH3. The color disappears on adding water, (d) A red color appears when PhjCCl reacts with Zn in C H. Oj decolorizes the solution. ... 

Esters of unsubstituted, polystyrene-bound trityl alcohol are too acid-sensitive to be useful for solid-phase synthesis [49]. Even treatment with alcohols or HOBt can lead to significant product release from the support. More stable towards solvolysis is... 

Polystyrene-bound allylic or benzylic alcohols react smoothly with hydrogen chloride or hydrogen bromide to yield the corresponding halides. The more stable the intermediate carbocation, the more easily the solvolysis will proceed. Alternatively, thionyl chloride can be used to convert benzyl alcohols into chlorides [7,25,26]. A milder alternative for preparing bromides or iodides, which is also suitable for non-benzylic alcohols, is the treatment of alcohols with phosphines and halogens or the preformed adducts thereof (Table 6.2, Experimental Procedure 6.1 [27-31]). Benzhy-dryl and trityl alcohols bound to cross-linked or non-cross-linked polystyrene are particularly prone to solvolysis, and can be converted into the corresponding chlorides by treatment with acetyl chloride in toluene or similar solvents (Table 6.2 [32-35]). 

Tris(7-methylnonyl) phosphite, t308 Trityl alcohol, t398 Tryptamine, a 170... 

The introduction and cleavage of the trityl ether proceeds through a very well-stabilised triphenylmethyl carbocation. In the case of trityl ether bond formation, the reaction is performed under anhydrous conditions and the carbocation, which is formed by an SN1 mechanism, reacts with an alcohol. In the case of cleavage, the triphenylmethyl carbocation ion is formed by treatment with acid, which is then trapped by water or a nucleophilic solvent to give trityl alcohol or other derivatives, respectively. Trityl ethers have also been used to protect thiols. 

Webster et al. l4a expanded on the preparation of the polyphenylenes to develop the one-pot synthesis of hyper-crosslinked poly(triphenylcarbinol). Thus, reaction of 4,4 -dilithiobiphenyl with (CH3)2C03 (— 80 °C — 25 °C, THF) afforded trityl alcohol-based polymer. The absence of carbonyl or methoxycarbonyl NMR resonances led to the speculation that the polymer grows via a branched convergent process. 

Fig. 2.21. Acid catalysed SN1 substitutions of trityl ethers to trityl alcohols, using deprotection procedures from nucleotide synthesis as an example. The table in the center indicates the time (t) it takes to completely cleave the respective trityl groups.

Trityl-based resins are highly acid-labile. The steric hindrance of the linker prevents diketopiperazine formation and the resins are recommended for Pro and Gly C-terminal peptides. Extremely mild acidolysis conditions enable the cleavage of protected peptide segments from the resin. These resins are commercially available as their chloride or alcohol precursors. The trityl chloride resin is extremely moisture-sensitive, so reagents and glassware should be carefully dried before use to avoid hydrolysis into the alcohol form. It is necessary to activate the trityl alcohol precursor and it is highly recommended to reactivate the chloride just before use see Note 4). After activation, attachment of the first residue occurs by reaction with the Fmoc amino acid derivative in the presence of a base. This reaction does not involve an activated species, so it is free from epimerization. Special precautions should be taken for Cys and His residues that are particularly sensitive to epimerization during activation (Table 2). 

Also the trityl group was applied for the masking of SH functions. The sulfides were prepared by the reaction of the thiol with trityl chloride (75% yield) or from trityl alcohol and the thiol in the presence of anhydrous TFA (85-90% yield). The cleavage of this group can be carried out under several conditions (Scheme 58). It is sensitive to acids (e.g. trifluoroacetic acid/ethanethiol 1 1) and to heavy metals. Thiocyanogen (SCN)2 oxidizes 5-trityl ethers to the disulfides and iodine converts 5-tritylcy -teine derivatives to cystine structures. 

Sodium perborate, toluene, reflux, 2-lOh, 81-91% yield. Even trityl alcohol will participate in this reaction in moderate yield. ... 

A C2-symmetric homochiral diol 13 (DHPEX) is a chiral proton source developed by Takeuchi et al., for samarium enolates which are readily prepared by Sml2-mediated allylation of ketenes [25,26]. In the stoichiometric reaction using DHPEX 13, they found that -45 C was the best reaction temperature for the enantioface discrimination, e.g., when methyl (1-methyl-l-phenylethyl)ketene 55 was used as a substrate, the product exhibited 95% ee [27]. The catalytic reaction was carried out using trityl alcohol as an achiral proton source which was added to a mixture of in situ generated samarium enolate 56 and DHPEX 13 (0.15 equiv) slowly so as not to exceed the ratio of the achiral proton source to DHPEX 13 of more than 0.7. The highest ee (93% ee) of product 57 was gained when the achiral proton source was added over a period of 26 h (Scheme 8) [27]. 

At the outset of this work, only the parent compound 3 was known, having been synthesized from the corresponding trityl chloride and acetylene bis-Grignard. However, the formation of trityl acetylenes from trityl alcohols was generally well established. Thus, it appeared that this class of compounds would be easily accessible. 

The simplest approach to sensor 20 was to start with the diamine recognition elements in place.Thus, trityl alcohol 24a was prepared in three steps from ethyl aminobenzoate as shown in Scheme 10. Conversion of the trityl alcohol to the trityl acetylene was attempted using the typical procedure. Unfortunately, the diamine recognition elements did not survive these conditions, yielding only decomposition, though a variety of permutations were explored. A similar fate was met with several potential precursors to the desired diamine appended trityl acetylene (e.g., 24b and... 

Intermediate 31 was synthesized as shown in Scheme 13. Trityl alcohol 32 was prepared from ester 22 and was smoothly converted to trityl acetylene 33. Glaser coupling of compound 33 gave the tetra-anisole intermediate 31 in good yield. We found that the sulfonanilide group... 

Scheme 17 depicts the synthesis of the first generation carbohydrate sensor. The trimethylsilyl appended trityl alcohol 43 was prepared by the standard method. Conversion of 43 to the trityl acetylene and mono-Sonogashira coupling gave the first half of the receptor (45). Trityl acetylene 47 was constructed in the standard fashion from trityl alcohol... 

These resins are extremely moisture sensitive, and so it is essential that all reagents and glassware should be dried thoroughly before use. 2-Chlorotrityl chloride resin can be stored desiccated at room temperature 4-(chloro-(diphenyl)methyl)benzoyl resins should be generated from the precursor trityl alcohol immediately before use as described in Protocol 5. The chemical characteristics of 7 and 8 are identical. 

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