Deprotection temperature

Thus, we have chosen the alternating copolymer of DMBZMA with MST as our resist material for its high thermal stability (Tg=210°C). TGA curves of the DMBZMA-MST copolymers are compared with that of PDMBZMA in Figure 5. Although incorporation of MST does not affect the deprotection temperature, the copolymers exhibit lower main chain stability than PMAN (PDMBZMA becomes PMAN above 260°C) and behave like PMMA and poly(a-methylstyrene) in terms of their main chain stability. 

Thermal analyses provide guidance as to at what temperature a resist film should be baked after coating. The PAB temperature must be below a deprotection temperature in the case of positive resists based on acid-catalyzed deprotection but should be preferably higher than its Tgto minimize the free volume in the film, as discussed earlier. 

A thermogravimetric analysis (TGA) profile of a typical alicyclic copolymer resist resin, poly(CBN-co-NBCA), is shown in Fig. 7.15. All of the alicyclic resist co-and terpolymers show similar TGA profiles. The deprotection temperature and decomposition temperature for the polymers are roughly 250°C and 400°C, respectively. At the deprotection temperature, roughly 25% weight loss associated with the deprotection event and corresponding to the loss of isobutylene and carbon... 

The thermal deprotection temperatures (T ) of the t-Bu protected polymers P(t-BuOMI/X-St), TgS of the deprotected polymers P(HOMI/X-St), and the onset decomposition temperatures (T ) of the deprotected poljroers were measured in nitrogen atmosphere and are summarized in Table II. Tie amounts of weight loss of the protected copolymers during the thermal deprotection measured by TGA agreed well with the calculated amounts. All the t-BuOMI copolymers are deprotected at about 270 or above and the deprotected polymers KHOMI/X-St) having HOMI units showed high TgS of about 245 °C or no Tg observed. 

BuOMl/X-St), t-BuOMI units are converted into W-hydroj maleimide (HOMI) units in the deprotected copolymers P(HOMI/X-St). Measured in wt % by TGA and theoretical calculation. Tdp is the deprotection temperature measured in the first run of DSC (cf. Fig. 2). is the glass transition temperature of the deprotected copolymer measured in the second run of DSC (cf. Fig. 2). Tdc is the onset decomposition temperature of main-chains measured by TGA. t-BOCSt units are converted to p-hydro5Q tyrene (HOSt) units by releasing carbone dioxide and 2-methylpropene (ref. 3). 

In other work, the impact of thermal processing on linewidth variation was examined and interpreted in terms of how the resist s varying viscoelastic properties influence acid diffusion (105). The authors observed two distinct behaviors, above and below the resist film s glass transition. For example, a plot of the rate of deprotection as a function of post-exposure processing temperature show a change in slope very close to the T of the resist. Process latitude was improved and linewidth variation was naininiized when the temperature of post-exposure processing was below the film s T. 

Q, 9/3,9n/3)]-9-(Benzyloxycarbonylamino)-6-oxoperhydropyrido[2,l-Z)][l, 3]thiazine-4-carboxylic acid was obtained from the methyl ester by treatment with 2 N LiOH in MeOH at 0°C for 4.5 h. The carboxyl group was coupled with amino esters. The 9-(benzyloxycarbonylamino) group was deprotected by treatment with a 1 1 mixture of TFA and CH2CI2 at room temperature and the amino group was acylated with an amino acid (97MIP4, 98USP5710129). 

RCM of a dienyne was also a key step in Mori s recent total synthesis of the alkaloid erythrocarine (447) [183]. The tetracyclic framework of447 was elaborated in the penultimate step, by exposing the hydrochloride of metathesis precursor 445 (1 1 diastereomeric mixture at the carbinol center) to first-generation catalyst A. The tandem process occurred smoothly within 18 h at room temperature leading to tetracycles 446 (1 1 mixture) in quantitative yield. Deprotection of the a-acetoxy isomer 446a led to 447 (Scheme 88). 

The synthesis of S-phosphonothiazolin-2-one 133 started with 2-bromothiazole 129. Nucleophilic displacement of the 2-bromide proceeded cleanly with hot anhydrous sodium methoxide to give 2-methoxythiazole 130. Low-temperature metalation of 130 with n-butyl lithium occurred selectively at the 5-position (76), and subsequent electrophilic trapping with diethyl chlorophosphate produced the 5-phosphonate 131. Deprotection of 131 was accomplished either stepwise with mild acid to pn uce the thiazolin-2-one intermediate 132, or directly with trimethylsilyl bromide to give the free phosphonic acid 133, which was isolated as its cyclohexylammonium salt. 

All of the ethynylated cyclobutadienes are completely stable and can be easily manipulated under ambient conditions, as long as the alkyne arms carry substituents other than H. For the deprotected alkynylated cyclobutadiene complexes, obtainable by treatment of the silylated precursors with potassium carbonate in methanol or tetrabutylammonium fluoride in THF, the stability is strongly dependent upon the number of alkyne substitutents on the cyclobutadiene core and the nature of the stabilizing fragment. In the tricarbonyUron series, 27b, 27c, 29 b, and 28b are isolable at ambient temperature and can be purified by sublimation or distillation under reduced pressure. The corresponding tetraethynylated complex 63 e, however, is not stable under ambient conditions as a pure substance but can be stored as a dilute solution in dichloro-methane. It can be isolated at 0°C and kept for short periods of time with only... 

Isolated yield. A, CFjOF in CCI3F at — 60 to — 80° with or without CaO B, F2 in Ar (or N2—CCI3F) at — 78° B, F2 in N2—HjO at room temperature C, Xep2-BF3 OEt2 in ether, benzene, toluene, dichloromethane, or a mixture of some of them (0° to room temperature). Yield of the deprotected compound after hydrolysis. " 2,2-Difluoro compound, Estimated from the final 2-deoxy-2-fluoroglycose. 

Enzymes are the catalyst per excellence for reactions in water, which is their natural habitat. Moreover, the use of enzymes often circumvents the need for functional group protection and deprotection steps. For example, enzymatic hydrolysis of penicillin G to 6-APA (Fig. 2.30) proceeds in one step at ambient temperature while chemical deacylation requires three steps, a temperature of - 40 C and various stoichiometric reagents, leading to a high E factor. 

The carbonyl group can be deprotected by acid-catalyzed hydrolysis by the general mechanism for acetal hydrolysis (see Part A, Section 7.1). A number of Lewis acids have also been used to remove acetal protective groups. Hydrolysis is promoted by LiBF4 in acetonitrile.249 Bismuth triflate promotes hydrolysis of dimethoxy, diethoxy, and dioxolane acetals.250 The dimethyl and diethyl acetals are cleaved by 0.1-1.0 mol % of catalyst in aqueous THF at room temperature, whereas dioxolanes require reflux. Bismuth nitrate also catalyzes acetal hydrolysis.251... 

The above section already introduced the influence of leaving groups at the benzylic position that eliminate to form and regenerate QM3, and the trend extends beyond adducts formed by the deoxynucleosides as expected. The standard benzylic acetate of QMP4 eliminates completely from the deprotected phenol under neutral aqueous conditions and ambient temperature within approximately 20 h, while an equivalent benzyl bromide eliminates completely within 5 min.48 Benzylic phosphates are also extremely labile, and, if the phosphate backbone of DNA is able to trap QM, the resulting products are likely to be too labile for standard detection.53,54 In contrast, amines and thiols are much less susceptible to elimination from the benzylic position and require forcing conditions to regenerate the parent QM.26,30 The benzylic alcohol derivative also appears stable under almost all thermal conditions and only eliminates routinely to form a QM after photochemical excitation.55... 

With this novel zinc chemistry, the protection and deprotection sequence were eliminated, the requirement of expensive cyclopropylacetylene was reduced from 2.2 to 1.2equiv and the previously required cryogenic temperature was eliminated. Finally, the overall yield was improved to 87% (in two steps) from 72% (in four steps). 

The deprotection of carbobenzyloxy protected phenylalanine was carried out in a low-pressure test unit (V= 200 ml) equipped with a stirrer, hydrogen inlet and gas outlet. The gas outlet was attached to a Non Dispersive InfraRed (NDIR) detector to measure the carbon dioxide. During the reaction the temperature was kept at 25 °C at a constant agitation speed of 2000 rpm. In a typical reaction run, 10 mmol of Cbz protected phenylalanine and 200 mg of 5%Pd/C catalyst were stirred in a mixture of 70 ml ethanol/water (1 1). The Cbz protected phenylalanine is not water-soluble but is quite soluble in alcoholic solvents conversely, the water-soluble deprotected phenylalanine is not very soluble in alcoholic solvents. Thus, the two solvent mixture was used in order to keep the entire reaction in the solution phase. Twenty p.1 of the corresponding modifier was added to the reaction mixture, and hydrogen feed was started. The hydrogen flow into the reactor was kept constant at 500 ml/minute and the progress of the reaction was monitored by the infrared detection of C02 in the off-gas. 

Two amino acid stereoisomers protected by benzyloxycarbonyl groups were deprotected in different ways. One isomer was hydrogenolyzed on 5% Pd/C (0.05 mol Pd/mol) in AcOEt-MeOH for 16 hours at ambient pressure and temperature. The other isomer was dissolved in MeOH, and cyclohexene (10 mol/mol) was added under nitrogen followed by 5% Pd/C (0.18 mol Pd/mol). The temperature was immediately raised to reflux, and stirring was continued for 7 minutes (Scheme 4.60).266... 

Enamine fragments present in quinolizine systems show their expected behavior as nucleophiles. For example, reaction of the indoloquinolizine derivative 78 with formaldehyde at room temperature afforded the unstable hydroxymethyl derivative 79, while reflux of 78 with formaldehyde under acidic conditions led to indole deprotection and allowed the isolation of the pentacyclic derivative 80 (Scheme 4) <2001TL7237>. 

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