Methyl acetate shielding

Figure 1-7 shows the separate NMR spectra of the protons and the carbons of methyl acetate (CH3CO2CH3). Although 98.9% of naturally occurring carbon is the nonmagnetic the carbon NMR experiment is carried out on the 1.1% of which has an / of Because of differential electronic shielding, the spectrum contains separate resonances... 

E.C. Sherer, G.M. Turner, and G.C. Shields, Investigation of the potential-energy surface for the first step in the alkaline-hydrolysis of methyl acetate, Int. J. Quantum Chem. (1995), pp. 83-93. 

Vinyl Acetate CH3COOCH=CH2 OH compds, HCN, Halides, Halogens, Mer-cap tans, Amine, Silanes Oxygen Vap in Air 2.6 to 13.4% > Ambient > Ambient Inhibitor—Methyl Ether of Hydroquinone or 3-5ppm Diphenylamine. Store in a dry, cool place shield from light impurities 20.9-21.5 402 427 Free-radical polymerization initiated by Benzoyl Peroxide... 

The number of investigations on the enantioselective dipolar cycloaddition of nitronates is still rather limited. In the case of simple alkyl nitronates, the facial selectivity is controlled solely by the steric environment about the two faces of the chiral unit. For example, the reaction of steroid dipolarophile 270 proceeds with the nitronate approaching the Re face of the alkene (Eq. 2.23) (234). The facial selectivity is controlled by the C(19) methyl group, which blocks the Si face of the dipolarophile. Similarly, exposure of 279 to ethyl acrylate at 40 °C for 24 h, provides a single nitroso acetal (Scheme 2.21) (242). The facial selectivity is presumed to arise from steric shielding by the menthol group, however the full stereostructure has not been established. 

Reaction of a methanolic solution of copper(II) acetate and enantiomerically pure (/ )/(S)-methyl( )-4ethyl-2-oxazolidinylidene)cyanoacetate 64 leads to the coordinatively unsaturated CVsymmetric intermediates (R,Rj-65 and (S,S)-65, which are sterically shielded at one side by two ethyl groups. Therefore, in contrast to the 2D- and 3D-coordination polymers, coordination of (R,R)/(S,S)-65 with only one cyano donor is possible, resulting in the formation of polymers (/>)-oc1[Cu(Li )2] (P-66) and (M)-J[Cu(L5)2] (M)-66) (Scheme 24) ([166, 169, 170] for other chiral lD-coordination polymers of our group, see [171, 172]). The X-ray crystal structure analysis of polymer (P)-66 clearly proves a well-ordered infinite onedimensional architecture. The central copper atoms in (P)- [Cu(L )2] CP-66) are almost tetragonal-pyramidally coordinated, and in contrast to the 2D- and... 

Epoxidation of vitamin D3 (38) is regio- as well as stereo-selective (equation 17). Though both C(S)—C(6) and C(7)—C(8) are trisubstituted double bonds reaction takes place selectively at C(7)— C(8), since only this route leads to the thermodynamically more stable conjugated diene derivative attack is selectively from the a-face since the 0-face is shielded by the axial methyl at C-13. Epoxidation of (39a) is stereoselective (equation 18). The selectivity is higher in (39a) than in the reaction of (39b R = MOM) due to stereoelectronic repulsive effects involving acetate and peroxy acid in the transition state leading to (41). 

Note 14). The vessel is placed behind a protective shield (Note 4) and immersed into a preheated oil bath at 160°C for 14 hr. After the solution is cooled to room temperature, solvent is removed with a rotary evaporator at aspirator vacuum and the crude residue is purified by silica gel chromatography (40% ethyl acetate-hexane) to give 2.8 g (70-75%) of tert-butyl 3a-methyl-5-oxo-2,3,3a,4,5,6-hexahydroindole-1-carboxylate as a white solid mp 112-113°C (Note 15). 

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