Z-Alkenyl iodides

The prochiral meso form of 2-cyclopenlen-1,4-diol (101) reacts with the (Z)-alkenyl iodide 102 to give the 3-substituted cyclopentanone 103 with nearly complete diastereoselectivity (98 2)[92], The reaction is used for the synthesis of prostaglandin. The alkenyl iodide 102 must be in the Z form in order to obtain the high diastereoselectivity. The selectivity is low when the corresponding (Z)-alkenyl iodide is used[93]. 

By contrast, when the first electrophile was an aldehyde as illustrated for the reaction of 276 with benzaldehyde, the resulting alkenylmetal presumably became part of a six-membered ring alkoxide 279 and hence so poorly reactive that it did not even react with iodine. However, treatment with Me3SiCl resulted in the silylation of the secondary zinc alkoxide and allowed iodinolysis to subsequently proceed, affording the (Z)-alkenyl iodide 280 (equation 132)165. Unfortunately, this protocol was not efficient for tertiary alkoxides generated by initial reaction of 276 with ketones. 

The (Z, , )-triene systems in leukotriene and DiHETE were constructed by the coupling of the (ZfT)-dienylborane with the (Z)-alkenyl iodide [129,130]. In the total synthesis of the naturally occurring large molecule palytoxin, which has numerous labile functional groups, Suzuki coupling gives the best results for the creation of the (E,Z)-, 3-diene part (290) by the coupling of the alkenylborane 288 with the (Z)-alkenyl iodide 289. In this case, thallium hydroxide as the base accelerates the reaction 1000 times more than KOH [131]. 

Additionally, in the elaboration of lactone 35 into key intermediate 11, mild conditions were employed to preserve the sensitive Z alkenyl iodide unit. The completion of synthesis from coupling product 11 was focused on the elaboration of the enyne side chain as well as the introduction of the chloride functionality. These transformations proceeded extremely well with an exception that the Peterson-type olefmation reaction provided only modest geometric selectivity ZIE = 6 1). 

Halogenation of vinylboranes generates vinyl halides. Both cis and trans halides are available by modification of the reaction conditions. When trans-alkenyl boronic acid (73, derived from 1-octyne) was treated with iodine and sodium hydroxide, trans-1-iodo-l-octene (74) was formed in 90%. When the boronic acid was treated with iodine and then with base, the (Z)-alkenyl iodide (75) was produced.Vinylboranes derived from internal alkynes lead to cis-trans mixtures with both of these procedures. Boronic acids derived from alkynes and catecholborane give the (Z)-bromide on addition of bromine followed by sodium hydroxide. ... 

In the total synthesis of (-)-gambierol, a marine polycyclic ether toxin, by two groups [28,29], the sensitive terminal (Z, Z)-triene side chain in 53 was constructed as a crucial step by stereoselective coupling of (Z)-alkenyl iodide 51 with (Z)-l,4-pentadienylstannane 52 in DMSO to afford 53 in 72% yield without isomerization of the triene system. Pd2(dba)3 and Cul as catalysts and TFP (1-3) as a ligand were used [29]. Similar coupling using the less reactive alkenyl bromide provided 53 in 43 % yield [28]. 

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