2-f-butyl-2- esters

The Z group can be hydrogenolyzed in the presence of other protective groups such as f-butyl ester, f-butyl ether, and iV-f-butoxycarbonyl (Boc) groups. f-Butyl esters are not affected by hydrogenation in the presence of palladium or platinum and are much more readily removed by acid catalysis (eq. 13.31).65... 

Diethyoxymethyldiphenylphosphine oxide. KETENE THIOACETALS Lithium iodide. a-KETO aldehydes Nafion-H. a-KETO esters f-Butyl hydroperoxide. Cy-anotrimethylsilane. 1,2-Diethoxy-1,2-disi-lyloxyethane. Trimethylphosphonoglyco-late. 

Several acids have been esterified by reaction with propene, " isobutylene, and ttimethylethylene. " The reaction is reversible and catalyzed by sulfuric acid or boron trifluoride. The optimum conditions for maximum conversion are low reaction temperature, large quantity of catalyst, and anhydrous conditions. " By this method, the keto ester, t-butyl o-benzoyl benzoate, " and the halo esters, f-butyl and isopropyl trichloroacetates,have been prepared. 

GLYCEROPHOSPHOLIPIDS 2,4,6-Triisopropylbenzenesulfonyl chloride. GLYCIDIC ESTERS f-Butyl chloro-acetate. 

Phthalocyanine sulfonic acids, which can be used as direct cotton dyes (1), are obtained by heating the metal phthalocyanines in oleum. One to four sulfo groups can be introduced in the 4-position by varying concentration, temperature, and reaction time (103). Sulfonyl chlorides, which are important intermediates, can be prepared from chlorosulfonic acid and phthalocyanines (104). The positions of the sulfonyl chloride groups are the same as those of the sulfonic acids (103). Other derivatives, eg, chlormethylphthalocyanines (105—107), / /f-butyl (108—111), amino (112), ethers (109,110,113—116), thioethers (117,118), carboxyl acids (119—122), esters (123), cyanides (112,124—127), and nitrocompounds (126), can be synthesized. 

Thiol esters, which are more reactive to nucleophiles than are the corresponding oxygen esters, have been prepared to activate carboxyl groups for both lactoniza-tion and peptide bond formation. For lactonization S-f-butyl and S-2-pyridyP esters are widely used. Some methods used to prepare thiol esters are shown below. The S-r-butyl ester is included in Reactivity Chart 6. 

TFA, phenol, 1 h, 45°, 73-93% yield. These conditions were developed for the mild cleavage of acid-sensitive esters of j3-lactam-related antibiotics, Diphenylmethyl and f-butyl esters were cleaved with similarly high efficiency. 

HCO2H, DCC, Pyr, 0°, 4 h, 87-90% yield." These conditions produce A-formyl derivatives of f-butyl amino acid esters with a minimum of racemization. 

Esters and amides may be sulfinylated. Addition of a mixture of t-butyl acetate and sulfinate ester 19 to a THF-ether solution of magnesium diisopropylamide led to the formation of (R)-(+)-f-butyl p-toluenesulfinylacetate (49) in 90% yield (equation 14)7. t-Butyl propanoate and butanoate also underwent this sulfinylation to give 50 and 51 in yields of 68 and 45%, respectively83. The diastereomeric ratio was 1 1 for 50 and 3 7 for 51. These esters may also be obtained by alkylation of 49. Similarly, treatment of a-lithio-A, A -dimethylacetamide with sulfinate ester 19 gave (R)-( + )-N, Ar-dimethyl-p-toluene-sulfinylacetamide (52) (equation 15)84. 

Some additions and corrections have been made. The data given here for f-butyl ethyl sulfoxide were not included in either Cox and Pilcher16 or Pedley, Naylor and Kirby17. The latter authors give data for a compound identified as ethyl methyl sulfate (sulfuric acid ethyl methyl ester), which is identified in Cox and Pilcher16 and in the original article23 as... 

Esterification of 22 with diol 24 (DCC/DMAP/BtOH) gave 29 in 84% yield (Fig. 12) and subsequent hydrolysis of the f-butyl ester group under acidic conditions afforded the third-generation carboxylic acid 23. All of the spectroscopic... 

Very low asymmetric induction (e.e. 0.3-2.5%) was noted when unsymmetrical sulphides were electrochemically oxidized on an anode modified by treatment with (—)camphoric anhydride or (S)-phenylalanine methyl ester . Much better results were obtained with the poly(L-valine) coated platinum electrodes . For example, f-butyl phenyl sulphide was converted to the corresponding sulphoxide with e.e. as high as 93%, when electrode coated with polypyrrole and poly(L-valine) was used. 

Entries 10 to 12 illustrate the use of organocopper conjugate addition in the synthesis of relatively complex molecules. The installation of a f-butyl group adjacent to a quaternary carbon in Entry 10 requires somewhat forcing conditions, but proceeds Transition Metals in ooc yie - I 1 Entry 11, the addition is to a vinylogous ester, illustrating the ability... 

Several biphenylphosphines with 2 -amino substituents are also effective in arylation of ester enolates.174 Among the esters that were successfully arylated were f-butyl acetate, /-butyl propanoate, and ethyl phenylacetate. The ester enolates were generated with LiHMDS. 

Among the most useful radical fragmentation reactions from a synthetic point of view are decarboxylations and fragmentations of alkoxyl radicals. The use of (V-hydroxy-2-thiopyridine esters for decarboxylation is quite general. Several procedures and reagents are available for preparation of the esters,353 and the reaction conditions are compatible with many functional groups.354 f-Butyl mercaptan and thiophenol can serve as hydrogen atom donors. 

As expected, other enol ethers work well in these procedures. For example, Jones and Selenski find that implementation of method F, which occurs by addition of MeMgBr to benzaldehyde 5 in the presence of dihydropyran (DHP) at 78 °C affords a 66% yield of the corresponding tricyclic ketal 59 with better than 50 1 endo diastereoselectivity (Fig. 4.31).27 On the contrary, Lindsey reports use of method H with the benzyl alcohol 35 and diethylketene acetal. The cycloaddition reaction occurs almost instantaneously upon deprotonation of the benzyl alcohol 35 by f-butyl-magnesium bromide in the presence of the ketene acetal and yields the corresponding benzopyran ortho ester 60 in a 67% yield.29... 

The urine samples were analyzed using a modified version of a published method.8 The method involved fortification of the urine samples with an internal standard 3,4,5-trichloro-2-pyridinyl, which is a structural isomer of the 3,5,6-TCP metabolite of chlorpyrifos hydrolysis of labile acid conjugates to 3,5,6-TCP solvent extraction derivitization to the f-butyl-dimethylsilyl ester of 3,5,6-TCP and subsequent negative-ion chemical ionization gas chromatography/mass spectrometry (GC/MS) analysis. Creatinine was determined in urine using a modification of a method of Fabiny and Erting-shausen.9... 

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

Double hydrophilic star-block (PEO-fo-PAA)3 copolymers were prepared by a combination of anionic and ATRP of EO and fBuA [150]. Three-arm PEO stars, with terminal - OH groups were prepared by anionic polymerization, using l,l,l-tris(hydroxymethyl)ethane, activated with DPMK as a trifunctional initiator. The hydroxyl functions were subsequently transformed to three bromo-ester groups, which were utilized to initiate the polymerization of f-butyl acrylate by ATRP in the presence of CuBr/PMDETA. Subsequent hydrolysis of the f-butyl groups yielded the desired products (Scheme 74). 

For the synthesis of permethric acid esters 16 from l,l-dichloro-4-methyl-l,3-pentadiene and of chrysanthemic acid esters from 2,5-dimethyl-2,4-hexadienes, it seems that the yields are less sensitive to the choice of the catalyst 72 77). It is evident, however, that Rh2(OOCCF3)4 is again less efficient than other rhodium acetates. The influence of the alkyl group of the diazoacetate on the yields is only marginal for the chrysanthemic acid esters, but the yield of permethric acid esters 16 varies in a catalyst-dependent non-predictable way when methyl, ethyl, n-butyl or f-butyl diazoacetate are used77). 

Palladium on charcoal, catalyst for reductive methylation of ethyl p-nitrophenylacetate, 47, 69 in reduction of /-butyl azidoacetate to glycine f-butyl ester, 45, 47 Palladium oxide as catalyst for reduction of sodium 2-nitrobcnzcne-sulfinate, 47, S... 

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