4-pentenyl iodide

Similarly, cyclizative tandem double-carbonylation reactions of 4-pentenyl iodide under irradiation conditions, is boosted by the addition of a catalytic amount of palladium complexes [72]. When performed in the presence of diethylamine, the carbonylation provided a triply carbonylated a,<5-diketo amide as the major product along with the doubly carbonylated y-keto amide (Scheme 6.48). Experimental evidence supports the interplay of two reactive species, radicals and organopalladium... 

A first study on the combination of transition metal catalysis with radical chemistry was published in 2002 by Ryu [158], Under CO pressure (40 atm), and in the presence of a palladium catalyst, cyclopentanones were formed from 4-pentenyl iodide in a photochemically initiated reaction. 

Cyclization and dicarbonylation of 4-pentenyl iodide afforded the keto ester 161 in 82 % yield in benzene in the presence of Pd(PPh3)4, Et3N, and DMAP at 100 °C and 40 atm under irradiation with a xenon lamp [72]. 

Dimethyl iodo(4-pentenyl)malonate (926) undergoes a Pd-catalyzed intramolecular radical-type reaction to form the alkyl iodides 927 and 928. rather than a Heck-type reaction product(775]. The same products are also obtained by a radical reaction promoted by tin hydride(776]. Although yield was low, a similar cyclization of the n-chloro ester 929 to form the seven-membered ring 930 was ob,served(777(. 

Butyllithium in pentane added to a well-stirred ice-cooled suspension of 1,2,3,6-tetrahydro-l,l-dimethyl-4-p-fluorophenylphosphorinium iodide in tetrahydrofuran, after 10-15 min. cyclohexanone in tetrahydrofuran added, and refluxed overnight -> (3-p-fluorophenyl-5-cyclohexylidene-3-pentenyl)dimethylphosphine oxide. Y 76%. F. e. s. D. Lednicer, J. Org. Chem. 3S, 2307 (1970). 

For the C2-acylated galactoside acceptor, a simple route begins with galactosyl bromide 41 (Scheme 8a). Orthoester formation required the use excess pentenyl alcohol and tetrabutylammonium iodide as promoter to obtain 42a and thence 42b. Acid-catalyzed reaction of the latter in the presence of excess pentenyl alcohol, then benzylidination gave acceptor 43a. The xylosyl acceptor 46b (Scheme 8b) was obtained similarly from bromide 44 via the n-pentenyl orthoester 45. Diol 46a was subjected to selective silylation at C4, paving the way to 46b. 

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