THP

Details are given in Table 3.3. As with all correlations, one should beware of using them if thp mea su ments taken are outside the region of the correlation that estabTishedthem. This method is commonly called ndM and is used mainly with vacuum distillates and lubricating oils. 

The oxidation of higher alkenes in organic solvents proceeds under almost neutral conditions, and hence many functional groups such as ester or lac-tone[26,56-59], sulfonate[60], aldehyde[61-63], acetal[60], MOM ether[64], car-bobenzoxy[65], /-allylic alcohol[66], bromide[67,68], tertiary amine[69], and phenylselenide[70] can be tolerated. Partial hydrolysis of THP ether[71] and silyl ethers under certain conditions was reported. Alcohols are oxidized with Pd(II)[72-74] but the oxidation is slower than the oxidation of terminal alkenes and gives no problem when alcohols are used as solvents[75,76]. 

Finally, a modification has been carried out in which a polyacrylate emulsion is added to a normal tetrakis(hydroxymethyl)phosphonium sulfate [55566-30-8] (THPS), urea, and TMM fire-retardant treatment in an attempt to completely alleviate the strength loss during the finishing. Indeed, better retention of tensile properties is achieved with no loss in fire resistance (85). 

THP—Amide Process. THP has also been made directly from phosphine [7803-5-27] and formaldehyde. The THP so generated contains one less mole of formaldehyde than either THPC or THPOH. It can be used in a THP—amide flame-retardant finish. The pad formulation contains THP, TMM, methylol urea, and a mixed acid catalyst (93—95). 

LRC-100Finish. The use of LRC-100 flame retardant for 50/50 polyester cotton blends has been reported (144). It is a condensation product of tetrakis(hydroxymethyl)-phosphonium salt (THP salt) and A/A7,A7 -trimethylphosphoramide [6326-72-3] (TMPA). The precondensate is prepared by heating the THP salt and TMPA in a 2.3-to-l.0-mole ratio for one hour at 60—65°C. It is appUed in conjunction with urea and trimethylolmelamine in a pad-dry-cure oxidation wash procedure. Phosphoms contents of 3.5—4.0% are needed to enable blends to pass the FF 3-71 Test. 

The identification of Tris as a potential carcinogen dealt a resounding blow to the flame-retardant finishing industry. From 1977 to 1984, several principal supphers of flame-retardant chemicals either reduced the size of their operations or abandoned the market completely. However, Albright and Wilson Corp. (UK) continues to produce THPC—urea precondensate and market it worldwide, and Westex Corp. (Chicago) continues to apply precondensate—NH finish to millions of yards of goods for various end uses. American Cyanamid reentered the market with a precondensate-type flame retardant based on THPS. 

Study on the carcinogenicity of THPC and THPS which concluded that there is no evidence of carcinogenic activity for either compound in rats or mice (162). 

Flame Retardants. The amount of research expended to develop flame-retardant (FR) finishes for cotton and other fabrics has been extremely large in comparison to the total amount of fabrics finished to be flame retardant. The extent of this work can be seen in various reviews (146—148). In the early 1960s, a substantial market for FR children s sleepwear appeared to be developing, and substantial production of fabric occurred. In the case of cotton, the finish was based on tetrakis(hydroxymethyl)phosphonium chloride (THPC) or the corresponding sulfate (THPS). This chemical was partly neutralized to THPOH, padded on fabric, dried under controlled conditions, and ammoniated. The finish was subsequently oxidized, yielding a product that passed the test for FR performance. This process is widely preferred to the THPOH—NH process. 

Me3SiBr, CH2CI2, 0°, 8-9 h, 80-97% yield.This reagent also cleaves the acetonide, THP, trityl, and r-BuMe2Si groups. Esters, methyl and benzyl ethers, r-butyldiphenylsilyl ethers, and amides are reported to be stable. 

CH3SCH3, CH3CN, (PhC0>202, 0°, 2 h, 75-95% yield. Acetonides, THP ethers, alkenes, ketones, and epoxides all survive these conditions. 

Benzyl, allyl, methyl, THP, TBDMS, and TBDPS ethers are all stable to these conditions. A primary MEM group could be selectively removed in the presence of a hindered secondary MEM group. 

The introduction of a THP ether onto a chiral molecule results in the formation of diastereomers because of the additional stereogenic center present in the tetrahy-dropyran ring (which can make the interpretation of NMR spectra somewhat troublesome at times). Even so, this is one of the most widely used protective groups employed in chemical synthesis because of its low cost, the ease of its installation, its general stability to most nonacidic reagents, and the ease with which it can be removed. 

MgBr2, Et20, rt, 66-95% yield.l-Butyldimethylsilyl and MEM ethers are not affected by these conditions, but the MOM ether is slowly cleaved. The THP derivatives of benzylic and tertiaiy alcohols give bromides. 

The THP ether can be converted directly to an acetate by refluxing in AcOH/AcCl (91 % yield). These conditions would probably convert other related acetals to acetates as well. The THP group can also be converted through the 0-SnBu3 to benzyl, MEM, benzoate, and tosylate groups. ... 

N HCl, EtOH, reflux, 90% yield for cholesterol. Although a direct stability comparison was not made, this group should be more stable than the THP group for the same reasons that the anomeric ethers of carbohydrates are more stable than their 2-deoxy counterparts. 

Ph2CHC02-2-tetrahydrofuranyl, 1% TsOH, CCI4, 20°, 30 min, 90-99% yield. The authors report that formation of the THF ether by reaction with 2-chlorotetrahydrofuran avoids a laborious proce ure that is required when dihydrofuran is used. In addition, the use of dihydrofuran to protect the 2 -OH of a nucleotide gives low yields (24-42%)." The tetrahydrofuranyl ester is reported to be a readily available, stable solid. A tetrahydrofuranyl ether can be cleaved in the presence of a THP ether. ... 

THF, Et3NHCe(ni) (N03)6, 50-100°, 8 h, 30-98% yield. Hindered alcohols give the lower yields. The method was also used to introduce the THP group with tetrahydropyran. 

The advantage of this ketal is that unlike the THP group, only a single isomer is produced in the derivatization. Conditions used to hydrolyze the THP group can be used to hydrolyze this acetal. This group may also find applications in the resolution of racemic alcohols. 

N HCl, THE, 0°, 100% yield. The ethoxyethyl ether is more readily cleaved by acidic hydrolysis than the THP ether, but it is more stable than the 1-methyl-1-methoxyethyl ether. 

Dichlorodicyanoquinone (DDQ), CH2CI2, H2O, 40 min, it, 84-93% yield.This method does not cleave simple benzyl ethers. This method was found effective in the presence of a boronate. The following groups are stable to these conditions ketones, epoxides, alkenes, acetonides, to-sylates, MOM ethers, THP ethers, acetates, benzyloxymethyl (BOM) ethers, and TBDMS ethers. 

The pixyl ether is prepared from the xanthenyl chloride in 68-87% yield. This group has been used extensively in the protection of the 5 -OH of nucleosides it is readily cleaved by acidic hydrolysis (80% AcOH, 20°, 8-15 min, 100% yield, or 3% trichloroacetic acid). It can be cleaved under neutral conditions with ZnBrj, thus reducing the extent of the often troublesome depurination of A -6-benzyloxy-adenine residues during deprotection. Conditions which remove the pixyl group also partially cleave the THP group (t,/2 for THP at 2 -OH of ribonucleoside = 560 s in 3% Cl2CHC02H/CH2Cl2). ... 

ACOH/H2O, (3 1), 35°, 10 min, 100% yield. An IPDMS ether is more easily cleaved than a THP ether. It is not stable to Grignard or Wittig reactions, or to Jones oxidation. 

Pyridine-HF, THF, 0-25°, 70% yield. Cyclic acetals and THP derivatives were found to be stable to these conditions. 

The direct conversion of a THP-protected alcohol to an acetate is possible, thus avoiding a deprotection step. ... 

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