Acetolysis derivatives

However, if reaction does involve bromine atoms as intermediates, one would expect to find products (including acetolysis) derived from addition of these radicals to the double bond, especially with olefms, such as norbornene, that possess unreactive allylic positions. Obviously the detailed mechanism of this reaction remains to be resolved. 

The 1-epivalidamine derivative 217 was prepared by successive azido-lysis, acetolysis, and hydrogenation of the dianhydride 216, derived from 51. 

Acetolysis of LXXIV gives, as might be expected, a mixture of the acetates of n-mannose and D-idose and as the dianhydro sugar has a free hydroxyl on C2, it should prove to be a source of 2-substituted n-mannose or D-idose and of 2,4-derivatives of n-mannose and 2,3-derivatives of D-idose. 

Introduction of a-substituents into the 3- or 7-position of 12a leads to a shift of the prevailing conformation from chair-chair (cc) to boat-chair (be), and finally to twist double boat (16) as judged by H NMR spectra (121). The changes in the H H coupling constants in these derivatives can be interpreted with skewed cc conformations as well. MM calculations, however, ruled out the latter possibility (121). The results of acetolysis of exo- and endobicyclo[3.3.1]nonan-3-yl tosylates were also interpreted with the aid of MM calculations (122). 

Cycloheptanes.— The C-1—C-2 bond in -y-thujaplicin is essentially single, Co"-/3-thujaplicin-amine complexes have been described, and thermodynamic data on the U -/3-thujaplicin complex have been calculated. The biomimetic cyclization of the silyl enol ether (191) to karahanaenone (192), using methyl-aluminium bis(trifluoroacetate) is almost quantitative (192) is also synthesized by thermolysis followed by desilylation of the silyl enol ether (193) which is readily available from l-bromo-2-methyl-2-vinylcyclopropane and isobutyraldehyde. Dehalogenation of 3-bromo-l-iodo-3-methylbutan-2-one with Zn-Cu couple on alumina in the presence of isoprene yields (192) and minor amounts of the isomers (194) and (195) however, dehalogenation with Fc2(CO)9 favours (195). Acetolysis of karahanaenol tosylate yields anticipated p-menthane derivatives and no filifolene. ... 

Byproducts of this rearrangement are cyclobutenes, cyclopropane derivatives and allenic alcohols. The ratio of these products depends on the substitution of the substrate and on the reaction conditions. For example, 3-methyl-5-tosyloxypenta-l,2-diene (3) gives 75% of 1-methyl-2-methylenecyclobutanol (4) upon hydrolysis with water and calcium carbonate at 100 °C, while acetolysis with acetic acid/sodium acetate at 80 °C, and subsequent treatment with lithium aluminum hydride, provides only 37% of the cyclobutanol.12... 

By acetolysis of a- or /3-methylene acetals of polyols with trifluoroacetic anhydride-carboxylic acid mixtures, derivatives may be prepared71 that are O-acylated at the primary hydroxyl group, and that have free hydroxyl groups at certain secondary positions. 

Efforts to cause the carbon nucleophile available at C-2 (carbohydrate numbering) of the osulose derivative 66 to displace the methoxy group with allylic rearrangement and with consequent formation of a tricyclic product by use of Pd(0) catalysts [34] were unsuccessful, but the intended reaction proceeds "smoothly when tin(IV) chloride is used together with acetic anhydride in dichloromethane. Clearly, the Lewis acid activates the allylic ether group, and the C-2 nucleophile effects its displacement. Concurrently, acetolysis of the benzylidene ring occurs and the product isolated is the cu-decalin analogue 67 [33],... 

Ring contraction was also noted on acetolysis of 3-tosyltetra-O- methyl-(+)-catechin the 2,3-dihydrobenzo[Z> ]furan formed can be oxidized to the benzo[f>]furan (Scheme 105) (66JCS(C)634). The 2-phenylbenzo[6]furan and its 2,3-dihydro derivative are degradation products of lignin and as such have been investigated extensively. 

Strong transannular sulfur participation is seen in the solvolysis of the p-nitrobenzoate of tetrahydrothiophene-2-methanol (574) the rate is 5.4x 107 times that of the corresponding cyclohexyl derivative. The product is a mixture of (577) and (578), arising through the episulfonium ion (576) (74T2087). The same mixture is also obtained under identical conditions from (575). Even more dramatic is the acetolysis of 2-endo-ch oxo-l -thiabicyclo[2.2.1]heptane, which is accelerated by a factor of 4.7 x 109 compared with the exo-chloro compound. The endo-chloro derivative leads stereospecifically to the endo-product via the sulfonium intermediate (Scheme 239) (75JA2886). 

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