Tcrt.-Butyl-

Ketone moschus (4-tcrt-butyl-2,6-dimethyl-3,5-dinitroacetophenone) [81-14-1] M 234.1, m 134-137 , 137-138 . Purified by recryst from MeOH. [Fuson et al. J Org Chem 12 587 1947.]... 

Di-tcrt-butyl dichlorosilane (DTBCI2) [18395-90-9] M 213.2, m -15°, b 190°/729mm, 195-197°/atm, d 1.01. Purified by fractional distn. It is a colourless liquid with a pleasant odour and does not fume in moist air, but does not titrate quantitatively with excess of dil alkali. [7 Am Chem Soc 70 2877 1948.]... 

Di-tcrt-butyl silyl bis(trifluoromethanesulfonate) [85272-31-7] M 440.5, b 73.5-74.5°/0.35mm, d 1.36 (see pK for triflic acid). Purified by fractional distillation. It is a pale yellow liquid which should be stored under argon. It is less reactive than the diisopropyl analogue. The presence of the intermediate monochloro compound can be detected by H NMR, (CHCI3) rer/-Bu2Si(OT02 [5 l -25s] but... 

In addition to stabilisers, antioxidants and ultra-violent absorbers may also be added to PVC compounds. Amongst antioxidants, trisnonyl phenyl phosphite, mentioned previously, is interesting in that it appears to have additional functions such as a solubiliser or chelator for PVC insoluble metal chlorides formed by reaction of PVC degradation products with metal stabilisers. Since oxidation is both a degradation reaction in its own right and may also accelerate the rate of dehydrochlorination, the use of antioxidants can be beneficial. In addition to the phenyl phosphites, hindered phenols such as octadecyl 3-(3,5-di-tcrt-butyl-4-hydroxyphenyI)propionate and 2,4,6-tris (2,5-di-rcrt-butyl-4-hydroxybenzyl)-1,3,5-trimethylbenzene may be used. 

Table 2. Reaction of Tributylmethylphosphonium Fluoride and 2-tcrt-Butyl-3-Chlorooxirane [27]...

Step 3 Capture of tcrt-butyl cation by chloride ion ... 

The molecularity of an elementary step is given by the number of species that undergo a chemical change in that step. Transfer of a proton from hydrogen chloride to tcrt-butyl alcohol is bimolecular because two molecules [HCl and (CH3)3COH] undergo chemical change. 

The first step of this new mechanism is exactly the sane as that seen earlier for the reaction of tcrt-butyl alcohol with hydrogen chloride—fonnation of an alkyloxonium ion by proton transfer from the hydrogen halide to the alcohol. Like the earlier example, this is a rapid, reversible Brpnsted acid-base reaction. 

The major difference between the two mechanisms is the second step. The second step in the reaction of tcrt-butyl alcohol with hydrogen chloride is the unimolecular dissociation of tcrt-butyloxonium ion to tcrt-butyl cation and water. Heptyloxonium ion, however, instead of dissociating to an unstable primar y car bocation, reacts differently. It is attacked by bromide ion, which acts as a nucleophile. We can represent the transition state for this step as ... 

Osrnate esters are fairly stable but are readily cleaved in the presence of an oxidizing agent such as tcrt-butyl hydroperoxide. 

Acid-catalyzed addition of alcohols to alkenes is sometimes used. Indeed, before its use as a gasoline additive was curtailed, billions of pounds of tcrt-butyl methyl ether (MTBE) was prepared by the reaction ... 

The rearrangement with ring contraction probably is the most important synthetic application of the Favorskii reaction it is for example used in the synthesis of steroids. Yields can vary from good to moderate. As solvents diethyl ether or alcohols are often used. With acyclic a-halo ketones bearing voluminous substituents in a -position, yields can be low a tcrt-butyl substituent will prevent the rearrangement. 

As a side reaction, the Norrish type I reaction is often observed. The stability of the radical species formed by a-cleavage determines the Norrish type 1/Norrish type II ratio. For example aliphatic methyl ketones 10 react by a Norrish type II-mechanism, while aliphatic tcrt-butyl ketones 11 react preferentially by a Norrish type I-mechanism. 

The asymmetric epoxidation of an allylic alcohol 1 to yield a 2,3-epoxy alcohol 2 with high enantiomeric excess, has been developed by Sharpless and Katsuki. This enantioselective reaction is carried out in the presence of tetraisopropoxyti-tanium and an enantiomerically pure dialkyl tartrate—e.g. (-1-)- or (-)-diethyl tartrate (DET)—using tcrt-butyl hydroperoxide as the oxidizing agent. 

In order to induce the free-radical chain reaction, a starter compound such as dibenzoyl diperoxide, azo-Zj -(isobutyronitrile) or tcrt-butyl hydroperoxide or UV-light is used. The commercially available, technical grade N-bromosuccinimide contains traces of bromine, and therefore is of slight red-brown color. Since a small amount of elemental bromine is necessary for the radical... 

Inductive effects (Section 16.4) are also important in determining alcohol acidities. Electron-withdrawing halogen substituents, for example, stabilize an alkoxide ion by spreading out the charge over a larger volume, thus making the alcohol more acidic. Compare, for example, the acidities of ethanol (p/

The above strategy was tested [27] with a 3-layer LED consisting of a poly(2,5-thienylene vinylene) (PTV) layer, known to have particularly low oxidation potential [28], followed by a layer of l,4-fcrs-(4 -diphenylaminostyryl)-2,5-di-methoxy-benzene (DASMB) [29] and a layer of 2-(4-biphenyl)-5-(4-tcrt-butyl-pheenyl)-1,3,4-oxadiazol (PBD) dispersed in polystyrene (PS) in a 20 80 ratio. Films of poly-(2,5-thienylene-a-bromoethylcne) were obtained by vapor phase pyrolysis of 2,5-W.v-(bromomethyl)lhiophcne and subsequent vapor deposition of the quinoid monomers onto a cold substrate following a previously published procedure [30]. They were converted to PTV by temperature-induced elimination of HBr. 

R = H methyl (R)-2-tcrt-butyl-5-formyl-2,3-diliydro-3-oxazolecarhoxylute yield 75%... 

Butyl- 285 tcrt.-Butyl- 619 tert.-Butylthio- 500 Chlor- 557 subst. 406... 

The sole recent example in this category is the condensation (in hot aqueous ethanolic sodium hydrogen carbonate) of o-phenylenediamine (399) with tA-tert-butyl 2-hydroxy-3-oxo-l,2,6-piperidinetricarboxylate (400) to give tcrt-butyl 3-[3-(tcrt-butoxycarbonyl)-3-(tcrt-butoxycarbonylamino)propyl]-2-quinoxalinecarboxy-late (401) in 87% yield. ... 

Carboxylic acids can be converted to tcrt-butyl esters by treatment with tert-hvXy ... 

All classes of primary amine (including primary, secondary, and tertiary alkyl as well as aryl) are oxidized to nitro compounds in high yields with dimethyl dioxirane." Other reagents that oxidize various types of primary amines to nitro compounds are dry ozone, various peroxyacids," MeRe03/H202,"" Oxone ," ° tcrt-butyl hydroperoxide in the presence of certain molybdenum and vanadium compounds, and sodium perborate." ... 

C10H13NO2 17831-01-5) see Ramipril Spirapril L-alanine tcrt-butyl ester... 

One other reaction deserves mention. From bis(cyclooctadiene)nickel and butadiene (31), and in the presence of an isocyanide (RNC, R = cyclohexyl, phenyl, tcrt-butyl) two organic oligomeric products are obtained, 1 -acylimino-11 -vinyl-3,7-cycloundecadiene and 1 -acylimino-3,7,11 -cyclo-dodecatriene. In each, one isocyanide has been incorporated. An analogous reaction with carbon monoxide had been reported earlier. The proposed mechanism of these reactions, via a bis-7r-allyl complex of nickel, is probably related to the mechanism described for allylpalladium complexes above. 

Steffan RJ, K McClay, S Vainberg, CW Condee, D Zhang (1997) Biodegradation of the gasoline oxygenates methyl ferf-butyl ether, ethyl ferf-butyl ether, and amyl tcrt-butyl ether by propane-oxidizing bacteria. Appl Environ Microbiol 63 4216-4222. 

Smith CA, MR Flyman (2004) Oxidation of methyl tcrt-butyl ether by alkane hydroxylase in dicyclopro-pyUcetone-induced and n-octane-grown Pseudomonas putida Gpol. Appl Environ Microbiol 70 4544-4550. 

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