1,8-Additions to Troponoid Systems: A Novel Route to Substituted Cycloheptadienes

trans-6-Aminocyclohept-3-enols, a New Designed Polyfunctionalized Chiral Building Block for the Asymmetric Synthesis of 2-Substituted-4-hydroxypiperidines

“…The meso -substrates 9 and 10 were prepared, in line with established literature precedents, , from commercially available tropone ( 11 ) (Scheme ).

2 Synthesis of m eso -Precursors 9 and 10 a a Reagent and conditions: (a) NaBH 4 , MeOH/H 2 O, rt, 88%; (b) MCPBA, CH 2 Cl 2 /H 2 O−NaHCO 3 , 0 °C, 94%; (c) LiAlH 4 , THF, rt, 80%; (d) Ac 2 O, pyridine, rt, 99%.

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Rearrangement of Quadricyclanone. Genesis of the cis-Bicyclo[3.2.0]heptadiene System

“…Reduction of 3 with lithium aluminum tri-Z-butoxy hydride, however, yielded neither of these alcohols, but gave, as the major product (61%), ds-bicyclo[3.2.0]-6-hepten-2-one (8, infrared (neat, µ): 3.31 (w), 3.41 (m), 5.78(s), and 13.80 (s)) along with a small amount (9%) of the corresponding alcohol, <?zzifo-cM-bicyclo[3.2.0]-6-hepten-2ol (9).12 This reaction constitutes, as far as we can determine, the first example in which only the double bond of an ,ß-unsaturated ketone is reduced by this reagent, although lithium aluminum hydride has been used to achieve similar results in some special cases. 13 We have concluded, after examination of Dreiding molecular models, that the carbonyl of 3 is not reduced by lithium aluminum tri-?-butoxy hydride because it is sterically hindered by the four-membered ring; i.e., the reagent is too bulky for endo approach to the carbonyl and the salt resulting from exo approach of the hydride donor cannot be accommodated in the endo position. Consequently, exo hydride donation in the ß-position is favored, yielding the enolate anion which is subsequently hydrolyzed to the ketone (8).…”

“…Thus the normality of acetylcholinesterase active sites may be determined in an accurate and convenient manner.15 (12) This equation follows that for a method B titration of a-chymotrypsin with N-frarcs-cinnamoylimidazole. 13 It should be noted that a dilution factor was mistakenly omitted in that previous equation. (14) Results consistent with those of Table I were obtained when the titration was determined at pH 8.20 at an enzyme concentration of 1.49 X 10-6 N.…”

Stereochemistry of the reduction of homobenzyl halides

“…; (b) S. J. Cristol and A. L. Noreen, ibid., 91, 3969 (1969). (6) (a) R. W. Fessenden and R. H. Shuler, J. Chem. Phys., 39, 2180 (1963); (b) P. Bakuzis, J. K. Kochi, and P. J. Krusic, J. Amer.…”