Butylate configuration

Griesbeck and Mattay described photocycloaddition of methyl and ethyl trimethyl pyruvates (25) with di-isopropyl-1,3-dioxol. In contrast to the reaction with ethyl pyruvate, the bicyclic oxetane 26 was formed with very high (>98%) diastereoisomeric excess (Sch. 7) [29]. An X-ray analysis revealed the unusual endo-tert-butyl configuration. Semiempirical calculation indicated that this clearly is the kinetic product formed by a biradical... 

Table 2. Regioselectivity and enantiomeric excess as a function of photolysis medium and sec-butyl configuration.

Butyl alcohols encompass the four stmcturaHy isomeric 4-carbon alcohols of empirical formula C H qO. One of these, 2-butanol, can exist in either the optically active R — ) or configuration or as a racemic ( ) mixture [15892-23-6]. 

Butyl Rubber. In butyl mbber, isoprene is enchained by 1,4-addition ia the trans configuration (74). 

Azetidine, 7V-bromo-, 7, 240 Azetidine, AT-r-butyl- N NMR, 7, 11 Azetidine, AT-t-butyl-3-chloro-transannular nucleophilic attack, 7, 25 Azetidine, 3-chloro-isomerization, 7, 42 Azetidine, AT-chloro-, 7, 240 dehydrohalogenation, 7, 275 Azetidine, 7V-chloro-2-methyl-inversion, 7, 7 Azetidine, 3-halo-synthesis, 7, 246 Azetidine, AT-halo-synthesis, 7, 246 Azetidine, AT-hydroxy-synthesis, 7, 271 Azetidine, 2-imino-stability, 7, 256 Azetidine, 2-methoxy-synthesis, 7, 246 Azetidine, 2-methyl-circular dichroism, 7, 239 optical rotatory dispersion, 7, 239 Azetidine, AT-nitroso-deoxygenation, 7, 241 oxidation, 7, 240 synthesis, 7, 246 Azetidine, thioacyl-ring expansion, 7, 241 Azetidine-4-carboxylic acid, 2-oxo-oxidative decarboxylation, 7, 251 Azetidine-2-carboxylic acids absolute configuration, 7, 239 azetidin-2-ones from, 7, 263 synthesis, 7, 246... 

Neopentyl (2,2-dimethylpropyl) systems are resistant to nucleo diilic substitution reactions. They are primary and do not form caibocation intermediates, but the /-butyl substituent efiTectively hinders back-side attack. The rate of reaction of neopent>i bromide with iodide ion is 470 times slower than that of n-butyl bromide. Usually, tiie ner rentyl system reacts with rearrangement to the /-pentyl system, aldiough use of good nucleophiles in polar aprotic solvents permits direct displacement to occur. Entry 2 shows that such a reaction with azide ion as the nucleophile proceeds with complete inversion of configuration. The primary beiuyl system in entry 3 exhibits high, but not complete, inversiotL This is attributed to racemization of the reactant by ionization and internal return. 

Other mechanisms must also operate, however, to account tor the fact that 5-10% of the product is formed with retained configuration at the chiral center. Isotopic labeling studies have also demonstrated that the 3-bromo-2-butyl radical undergoes reversible loss of bromine atom to give 2-butene at a rate which is competitive with that of the bromination reaction ... 

A study of the photolysis of A, B, and C has been reported. A gives both D and the cleavage product benzaldehyde. B gives only E. C gives benzaldehyde and the stereoisomer B. Discuss the ways in which the presence and configuration of the remote t-butyl group can control the product composition, and account for the formation of the observed products. 

High vacuum sublimation of the 3-monobenzoate of (32) or tosylchloride dehydration gives 3/ -benzoyloxy-7-methylenecholest-5-ene (33). The configuration of (32) is probably as shown since 7a-hydroxy steroids dehydrate readily to yield homoannular dienes. In an analogous reaction ethyl and iso-butyl Grignard reagents give alkylidene compounds as the only isolated products. 

AC2O, FeCl3, Et20, 76-93% yield." These conditions give the acetate of the alcohol, which can then be cleaved by simple basic hydrolysis. The method is also effective for the conversion of r-butyl glycosides to acetates with retention of configuration (80-100% yield). 

As shovm above, the attachment of the aromatic ring to the carbon chain bearing the basic nitrogen may be accomplished through an ester or an amide configured in either direction. A simple ether linkage fulfills this function in yet another compound that exhibits local anesthetic activity. Thus, alkylation of the mono potassium salt of hydroquinone with butyl bromide affords the ether (77) alkylation of this with w-C3-chloropropyl)morpholine affords pramoxine (78)... 

The configuration of the adduct with dimethyl acetylenedicarboxylate depends on the nature of the solvent used protic solvents, such as methanol or ethanol (but not tert-butyl alcohol), favor formation of (Z)-25a, whereas in nonprotic solvents, such as benzene, chloroform or acetonitrile, ( )-25a is the major product. 

Molander and Mautner demonstrated that deprotonation of cis-a, 3-epoxysilane 150 with s-BuLi/TMEDA was complete in 10 minutes, whereas the corresponding trows-isomer 150 required 4 hours [56]. Similarly, treatment with butyraldehyde was more efficient with cis-151 (Scheme 5.35), which could also be trapped with a wide variety of other carbonyl-containing electrophiles. The results demonstrated that lithiated epoxides cis- and trons-151 were configurationally stable at -116 °C for periods of up to 4 hours. Only in the case of cis-151 (t-butyl = n-octyl) was the lithiated epoxysilane found to be configurationally unstable. 

Chemical structure. The structure of the free base of Cypridina luciferin (C22H27ON7, Mr 405.50) was determined by Kishi et al. (1966a,b) as shown below (A) its sec-butyl group is in the same configuration as in L-isoleucine. The structure of oxyluciferin reported by the same authors contained an error, and the structure was corrected later as shown in Fig. 3.1.8 (McCapra and Chang, 1967 Stone, 1968). 

Treatment of m-butyl (S )-4-formyl-2,2-dimethyl-3-oxazolidinccarboxylate ( Garner aldehyde, 3), readily available from /V-Boc-l-serine and configurationally extremely stable49,50, with various nucleophiles preferentially yields the n n(nonchelation)-diastereomeric amino alcohols 4 in high chemical yield51 -55,57-61. 

A comparison of the configuration of the substrates and reaction products shows that the oxiranyl anions arc configurationally stable under the reaction conditions. Only one example is known in which isomerization was observed. When the ci.v-tm-butyl-substituted epoxysilane27 was metalated and quenched with 2-cyclohexenone, addition product 27 was obtained under inversion of the anionic center. Presumably the strain created in forcing the ter/-butyl and the trimethylsilyl group cis on the oxirane ring facilitates the isomerization process13. 

Lithium and zinc tert-butyl phenylmethyl sulfoxide (1) and A-phenyl imines 2, in which the substituent R is alkenyl or aryl, react at —78 °C over 2 hours with high anti diastereoselection (d.r. >98.5 1.5)6. Shorter reaction times result in poorer yields, due to incomplete reaction. In contrast, the reaction of the sulfoxide anion with benzaldehyde is complete after 5 seconds, but shows poor diastereoselection. When the substituent R1 or R2 of the imine 2 is aliphatic, the substrates exhibit poor chemical reactivity and diastereoselection. The high anti diastereoselection suggests that if a chelated cyclic transition state is involved (E configuration of the imine), then the boat transition state 4 is favored over its chair counterpart 5. 

The addition of the anion of the 1,3-dimethyl-2-butenyl sulfoxides to 2-cyclopentenone was examined2. The anion of rar-2-methyl-4-(phenylsulfinyl)-2-pentene gave a 50 50 mixture of ( )- and (Z)-y-1,4-adducts which differed in the relative configuration of the new stereocenter regarding the stereocenter at sulfur. That is, for either the (Z)- or the ( )-product there is complete asymmetric induction from the stereocenter at sulfur, but in the opposite direction. When the rm-butyl analog, ruc-4-(/wt-butylsulfinyl)-2-methyl-2-pcntcne, was reacted, it gave exclusively the ( )-adduct, likewise as a single diastereomer. 

The lithium enolates of cyclopentanone and cyclohexanone undergo addition-elimination to the 2,2-dimethylpropanoic acid ester of ( )-2-nitro-2-hepten-l-ol to give 2-(l-butyl-2-nitro-2-propenyl)cycloalkanones with modest diastereoselection. An analogous reaction of the enolate ion of cyclohexanone with the 2,2-dimethylpropanoic acid ester of (Z)-2-nitro-3-phenyl-2-propenol to give 2-(2-nitro-l-phenyl-2-propenyl)cyclohexanones was also reported. The relative configuration of these products was not however determined6. 

The oxidation of a series of cyclic and acyclic sulphides by cytochrome P 450from rabbit liver gave sulphoxides with / -configuration at sulphur. The maximum of the e.e. value (53.8%) was observed for benzyl t-butyl sulphoxide310. 

Optically pure (S)-benzyl methyl sulfoxide 139 can be converted to the corresponding a-lithio-derivative, which upon reaction with acetone gave a diastereomeric mixture (15 1) of the /S-hydroxysulfoxide 140. This addition reaction gave preferentially the product in which the configuration of the original carbanion is maintained. By this reaction, an optically active epoxy compound 142 was prepared from the cyclohexanone adduct 141181. Johnson and Schroeck188,189 succeeded in obtaining optically active styrene oxide by recrystallization of the condensation product of (+ )-(S)-n-butyl methyl sulfoxide 143 with benzaldehyde. 

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