Allylation of epoxides with allylic indium reagents

Organoindium Reagents: The Preparation and Application in Organic Synthesis

“…This result is in agreement with the report from Pae and co-workers who demonstrated that, when a terminal vinyl epoxide was used as substrate, a consecutive 1,2-shift and regioselective allylation occurred to furnish homoallylic alcohol in reasonable yield (Scheme ) . In contrast, the use of tetraorganoindium reagents [(allyl) n Me (4– n ) InLi], which are postulated to behave like Lewis bases, reacted with styrene oxide in a different way to generate a mixture of products A and B (Scheme ) . It is noteworthy that a recyclable system using InCl and reusable heterogeneous mesoporous silica-supported palladium catalysts has also been developed by Li and co-workers for the same purpose …”

“…However, it seems that they wrongly assigned the structure of the major product A . In 2004, Hirashita, Araki, and co-workers reevaluated the reaction and found that, rather than the formation of a bishomoallyl alcohol A , a homoallylic alcohol C was formed exclusively under analogous conditions (Scheme ) . In view of the fact that Lewis acid (e.g., InCl 3 ) is capable of mediating the rearrangement of styrene oxide to phenylacetaldehyde, Hirashita and Araki proposed that the reaction presumably proceeded via an initial formation of the corresponding phenylacetaldehyde (facilitated by the Lewis acidity of the in situ-generated allylindium sesquihalide) followed by a subsequent allylation reaction.…”

“…In 2004, Hirashita, Araki, and co-workers reevaluated the reaction and found that, rather than the formation of a bishomoallyl alcohol A, a homoallylic alcohol C was formed exclusively under analogous conditions (Scheme 321). 521 In view of the fact that Lewis acid (e.g., InCl 3 ) is capable of mediating the rearrangement of styrene oxide to phenylacetaldehyde, 522 initial formation of the corresponding phenylacetaldehyde (facilitated by the Lewis acidity of the in situ-generated allylindium sesquihalide) followed by a subsequent allylation reaction. This result is in agreement with the report from Pae and co-workers who demonstrated that, when a terminal vinyl epoxide was used as substrate, a consecutive 1,2-shift and regioselective allylation occurred to furnish homoallylic alcohol in reasonable yield (Scheme 322).…”

Recent advances in allylindium reagents in organic synthesis

“…15 Compound 10 must be formed via the direct ring-opening reaction of styrene oxide by allylindium reagents; the spectroscopic data of 10 were, however, exactly matched with those of compound 12, which can be produced via the initial rearrangement of styrene oxide to phenylacetaldehyde and the successive allylation with allylindium reagents. 15 Later, Pae and co-workers extended the reaction to vinyl epoxides, such as, vinyloxirane and trans-cinnamyloxirane. 16 In these cases, rearrangement of the epoxide to the corresponding aldehyde occurred first via the ring-opening 1,2-hydride shift catalyzed by the Lewis-acidic allylindium species.…”

“…15 They also found that allylindium ate complexes can react directly with epoxides to give the ring-opening products to the contrary, as shown in Scheme 12. …”