2- Deuterio-2-methyl

Russell, G. A. Solvent effects in the reactions of free radicals and atoms. II. Effects of solvents on the position of attack of chlorine atoms upon 2,3-dimethylbutane, isobutane and 2-deuterio-2-methyl-propane. J. Amer. chem. Soc. 80, 4987 (1958). 

The normal coordinate analysis carried out using a program written by Hilder-brandt allowed one to deduce the best values for the force constants (within the simple valence molecular force field) for the species under consideration based on the observed vibrational frequencies. The observed and calculated frequencies are compared also. For instance, the observed v 5(CH3) and Vs(CH3) for [(CH3)4As] [(CH3)3GaCl] are equal to 2950 and 2846 cm" The corresponding calculated values are 2976 and 2862 cm" . In the case of the deuterio-methyl chlorometallate salt [(CH3)3AsCD3][CD3GaCl3] the observed values for Vas(CD3) and Vs(CD3) are 2238 and 2118 cm while the calculated ones are 2234 and 2076cm ... 

Because of the poor dispersion of the proton spectra of the methyl D-glucopyranosides in aqueous solution the above deuter-ation experiment only identified the methoxyl relaxation contribution into the H-l resonance. However, in the case of the corresponding tetra- acetates, all of the proton resonances were separately resolved and hence a direct comparison could be made of the non-selective Rj-values of all protons of the protio -and deuterio-methyl glycosides. As it happened, only the H-l and H-5 resonance evidenced any detectable relaxation contribution from the methoxyl group and these values are summarised in Table III. 

Moreover, the reaction of methyl acrylate and N nosylbenzaldimine, which was promoted by DABCO in the absence of la, was homogeneous in CHCI3 and proved amenable to kinetic analysis. The reaction was monitored by GC analysis, and was found to display a first order kinetic dependence on both DABCO and methyl acrylate. In contrast to the MBH reaction, rate saturation with respect to the imine electrophile was observed. A prominent primary kinetic isotope effect was also observed ka/ko = 3.81) by comparison of initial reaction rate of methyl acrylate with separate reactions of a deuterio methyl acrylate, strongly suggesting that deprotona tion of the a H(D) was rate limiting. 

A similar reaction the with rran.v-isomer 3b gave c -3,5-dimethylcyclohexene (4) with very high diastereoselectivity. Accordingly, the stereochemistry of this substitution is anti. Deuterium labeling experiments using the 1-deuterio or 3-deuterio derivative of 3 a showed that the ratio of SN2 /SN2 with lithium dimethylcuprate was about 50 50, while the ratio with lithium cyano(methyl)cupratc was >96 4. 

For the analysis of fatty acids amide-linked to GlcN(I), several chemical degradation procedures are available. One comprises periodate oxidation of 0-deacylated and 2H-reducedlipid A (lipid A-OH ). Following permethyl-ation, g.l.c.-m.s. analysis revealed a 2-deoxy-1 -deuterio-1,3-di-O-methyl-2-(iV-methyl-3-methoxyacylamido)glycerol derivative in which the amide-finked fatty acid at GlcN(I) was identified as 14 0(3-OH) in B. pertussis (93), and as 16 0(3-OH) and 18 0(3-OH) in R. trifolii 81). 

The electrophile E+ attacks the unhindered side of the still unsubstituted second aromatic ring. A proton (deuteron) is transferred from this ring to the second, originally substituted ring, from which it leaves the molecule. Thus, the electrophile enters, and the proton (deuteron) leaves the [2.2]paracyclophane system by the least hindered paths. Some migration of deuterium could be detected in the bromination of 4-methyl[2.2]paracyclophane (79). The proposed mechanism is supported by the kinetic isotope effects ( h/ d) found for bromination of p-protio and p-deuterio-4-methyl[2.2]paracyclophanes in various solvents these isotope effects demonstrate that proton loss from the a complex is the slowest step. 

In order to clarify the reaction mechanism, 6-deuterio-labeled 3,5-dinitro-l-methyl-2-pyridone (87, 1 mmol) was prepared and heated with cyclohexanone (2 mmol) and ammonia (10 mmol). A mixture of 2-deuterio- (88) and 4-deuterio-3-nitro-5,6,7,8-tetrahydroquinoline (89) was obtained in the ratio 58 42 (Scheme III.49). 

Berkessel and Sklorz screened a variety of potential co-ligands for the Mn-tmtacn/H202 catalyzed epoxidation reaction and found that ascorbic acid was the most efficient one. With this activator the authors could oxidize the terminal olefins 1-octene and methyl acrylate with full conversion and yields of 83% and 97%, respectively, employing less than 0.1% of the metal complex (Scheme 86). Furthermore, with E- and Z-l-deuterio-1-octene as substrates, it was shown that the oxygen transfer proceeded stereoselectively with almost complete retention of configuration (94 2%). Besides the epoxidation, also the oxidation of alcohols to carbonyl compounds could be catalyzed by this catalytic system (see also Section in.C). 

TITANOCENE-CATALYZED SYNTHESIS OF METHYL 4-DEUTERIO-4-PHENYL-4-HYDROXYBUTANOATE... 

Acetates. Because of the significant interest in selective acetylation reactions of sucrose, the need for a convenient and unambiguous method of identification has been recognized (34,35). The position of an acetyl group in a partially acetylated sucrose derivative can be ascertained by comparison of its H-nmr acetyl methyl proton resonances after per-deuterio acetylation with those of the assigned octaacetate spectrum. The synthesis of partially acetylated sucroses has generally been achieved either by way of selectively protected derivatives such as trityl ethers and cyclic acetals or by direct selective acetylation and deacetylation reactions. 

---