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Alkenes molecular transformation

Epoxides are useful synthetic intermediates, and the conversion of an alkene to an epoxide is often part of a more extensive molecular transformation.85 In many instances, advantage is taken of the high reactivity of the epoxide ring to introduce additional functionality. Because epoxide ring opening is usually stereospecific, such reactions can be used to establish stereochemical relationships between adjacent substituents. Such two- or three-step operations can accomplish specific oxidative transformations of an alkene that may not easily be accomplished in a single step. Scheme 12.13 provides a preview of the type of reactivity to be discussed. [Pg.772]

Senboku, H., Kajizuka, Y., Kobayashi, K., Tokuda, M., and Suginome, H., Photoinduced molecular transformations. 160. Furan annelation of 2-hydroxynaphthoquinone involving photochemical addition and radical fragmentation xeclusion of the intermediacy of [2-1-2] cycloadduct in a one-pot formation of furanoquinones by the regioselective 3-1-2 photoaddition of hydroxyquinones with alkenes. Heterocycles, 44, 341,1997. [Pg.1755]

H., and Kobayashi, K., Photoinduced molecular-transformations. 145. Regioselective [3-t2]-pho-toadditions of 2-hydroxyphenanthrene-l,4-dione with electron-rich alkenes and phenylacetylene... [Pg.1755]

Kobayashi, K., Takeuchi, H., Seko, S., Kanno, Y, Kujime, H., and Suginome, H., Photoinduced molecular transformations. 142. One-step synthesis of lff-benz[fjmdole-4,9-diones and IH-indole-4,7-diones by a regioselective photoaddition of 2-amino-l,4-naphthoquinones and 2-amino-1,4-benzoquinones with alkenes, Helv. Chim. Acta, 76, 2942, 1993. [Pg.1755]

Suginome, H., Liu, C.F., Seko, S., Kobayashi, K., and Furusaki, A., Photoinduced molecular transformations. 100. Formation of furocoumarins and furochromones via a P-scission of cyclobutan-oxyl radicals generated from [2-1-2] photoadducts from 4-hydroxycoumarin and acyclic and cychc alkenes. X-ray crystal structures of penta [3.4] cyclobuta [1,2-d] pyran-6(6aff)-one, cis- )-6b,8,9,9a-tetrahydro-6H,7H-cyclopenta[4,5]furo[3,2-c] [l]benzopyran-6-one, and c/s-l,2,2a,8b-tetrahydro-8b-hydroxy-l,l,2,2-tetramethyl-31T-benzo [b] cyclobuta [d] pyran-3-one, /. Org. Chem., 53, 5952, 1988. [Pg.2270]

Kobayashi, K., Suzuki, M., and Suginome, H., Photoinduced molecular transformations. 128. Regioselective [2-1-2] photocycloaddition of 3-acetoxyquinolin-2(lH)-one with alkenes and formation of furo [2,3-c] quinolin-4(5fd)-ones, l-benzazocine-2,3-diones, and cyclopropa [d] benz [1] azepine-2,3-diones via a P-scission of cyclobutanoxyl radicals generated from the resulting [2-1-2] photoadducts, /. Org. Chem., 57, 599,1992. [Pg.2271]

Another molecular transformation classified as click chemistry is the thiol-ene reaction (or alkene hydrothiolation) (Scheme 9.1b), which occurs between a thiol and an alkene to form an alkyl sulfide. It has all the desirable features of a click reaction, being highly efficient, simple to execute with no side... [Pg.288]

The adjacent iodine and lactone groupings in 16 constitute the structural prerequisite, or retron, for the iodolactonization transform.15 It was anticipated that the action of iodine on unsaturated carboxylic acid 17 would induce iodolactonization16 to give iodo-lactone 16. The cis C20-C21 double bond in 17 provides a convenient opportunity for molecular simplification. In the synthetic direction, a Wittig reaction17 between the nonstabilized phosphorous ylide derived from 19 and aldehyde 18 could result in the formation of cis alkene 17. Enantiomerically pure (/ )-citronellic acid (20) and (+)-/ -hydroxyisobutyric acid (11) are readily available sources of chirality that could be converted in a straightforward manner into optically active building blocks 18 and 19, respectively. [Pg.235]

Cobalt complexes derived from Schiff bases 388 catalyzed the hydroxyacylation of electron-deficient alkenes (Fig. 90) [431, 432]. Thus, methyl acrylate 387 reacted with aliphatic aldehydes 386 in the presence of 5 mol% of the in situ generated catalyst, molecular oxygen, and acetic anhydride to 2-acyloxy-4-oxoesters 389 in 56-77% yield. When acetic anhydride was omitted, the yields of products were lower and mixtures of the free hydroxy compounds and acylated compounds resulting from Tishchenko reactions were obtained. Electron-rich alkenes did not undergo the transformation, since the addition of the acyl radical is much slower. The acylcobalt species inserts oxygen instead and acts as an epoxidation catalyst. [Pg.295]


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See also in sourсe #XX -- [ Pg.75 ]




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