Epoxides, vinyl reaction with allylic alcohols

The regioselectivity in palladium-catalyzed alkylations has been attributed to the dynamic behavior of trihapto pentadienyl metal complexes60. For example, competing electronic and steric effects influence product formation in dienyl epoxides, but in palladium-catalyzed reactions steric factors were often found to be more important. Thus, alkylation of dienyl epoxide 76 with bulky nucleophiles such as bis(benzenesulfonyl)me-thane in the presence of (Ph3P)4Pd occurred exclusively at the terminal carbon of the dienyl system producing allyl alcohol 77 (equation 39). However, the steric factors could be overcome by electronic effects when one of the terminal vinylic protons was replaced with an electron-withdrawing group. Thus, alkylation of dienyl epoxide 78 affords homoal-lylic alcohol 79 as the major product (equation 40). 

Vinyl epoxides can be cross-coupled with vinylstannanes <2001JOC589>. This reaction proceeds through an (if-allyOpalladium complex (Equation 57) <2001JOC589>. Similar reactivity can be observed using bismuth reagents (Equation 58) <2001SC2365>. Vinyl oxiranes react with substituted allenes to form functionalized allyl alcohols <2004JOC4686>. 

In the presence of a palladium catalyst, allyl epoxides (113) react with nitrogen nucleophiles at the al-kenic carbon atom remote from the oxirane ring to give 1,4-adducts (114)." In the absence of a palladium catalyst, azide ion attacks the oxirane ring affording 1,2-adducts (115 Scheme 52 and Table 2)." Vinyl epoxide (116) gave 1,2- and 1,4-azido alcohol in a ratio of 1 1.5 irrespective of the reaction system. " Intramolecular cyclization of vinyl epoxide (117) in the presence of a palladium catalyst afforded isoquinuclidine (118 Scheme 52). ... 

Although some reactions, such as the transformation of -hydroxyalkyl selenides to -haloalkyl selenides (Scheme 161, b) or to vinyl selenides, enones (Scheme 161, 0. a,a-dihalocyclopropanes (Scheme 162, f) or p-hydroxyalkyl halides (Scheme 161, h Scheme 162, g), have bwn occasionally described or found only with specific types of -hydroxyalkyl selenides, especially those having a strained ring [e.g. their transformation to allyl selenides (Scheme 163, b), 1-selenocyclobutenes (Scheme 163, c) and cyclobutanones (Scheme 163, f),i2.i59,i60.i63] odiers are far more general. This is particularly the case of eir reductions to alcohols (Scheme 161, a Scheme 162, a Scheme 163, a Scheme 164, a Scheme 165, a) - or alkenes (Scheme 161, c Scheme 162, c Scheme 163, d Scheme 164, c Scheme 165, a Scheme 166, c), 89,i94,239 transformation to allyl alcohols (Scheme 161, e Scheme 162, b Scheme 164, b Scheme 166, b), - epoxides (Scheme 161, g Scheme 162, d Scheme 163, e Scheme 164, d Scheme 165, b Scheme 166, d) and rearranged carbonyl compounds (Scheme 162, e Scheme 164, e Scheme 165, a, c Scheme 166, e), - as well as oxidation to a-selenocarbonyl compounds (Scheme 161, d). 2 2.248-25i... 

The Sharpless cuid related epoxidation techniques (5 ) provide a way to control the stereochemistry of three neighboring carbons. The Cr(II) mediated reaction has been extended further to systems involving aldehydes and 2 2-diiodopropane (with HI loss) as well as vinyl iodides and bromides, all affording allylic alcohols ). ... 

---