The Facile Rearrangement of Vinyl 3-(Penta-1,4-dienyl) Ether

Catalysis of the Cope and Claisen rearrangements

“…Among the transition-metal derivatives employed as catalysts, ZnCl2 has been the most thoroughly studied, although rate accelerations are modest and the temperature requirements approach those of uncatalyzed rearrangements. The operation of a [3,3] process has been established in some cases, including the deuterated substrate, 136 (see above), which, upon treatment with 1 equiv of ZnCl2 in decalin at 120 °C for 7 h, yielded (32%) a mixture containing 151 (78%) and 152 (12%); the thermal reaction occurred at 180 °C.u3a In the rearrangement of 153, the observed product, 154 Other substrates that rearranged under similar conditions were: allyl phenyl ether (88%), p-Me (95%), m-Me (50% ortho product and 29% para product), and 2,4-Cl2 (36% + 30% cleavage phenol). As was the case with BC13 catalysis, electron-withdrawing substituents in the ring promoted the formation of cleavage phenols.…”

Stepwise intramolecular cycloaddition of nitrile oxide equivalents derived from the Lewis acid-promoted reaction of 1-nitroalkadienes and allylic stannanes

“…Reagents and conditions: i, (4), TiCl,, -78 "C to room temp., 2 h be the best catalyst for heterodiene [4 + 2]~ycloaddition,'~ treatment of diene (3h) with SnCl, (-78 "C; 1 h) gave compound (13) only in 49% yield. Fortunately, the aromatic compound (39 cyclised to give nitronate (14) in 80% yield, which in the presence of TiCl, reacted with allyltrimethylstannane (4) to give the dihydro-1,2-oxazine (15) in 30% yield [equation ( 3)]. Rather disappointingly, dihydro-1,2-oxazine derivatives could not be isolated from the reaction mixtures of dienes (3c-g) with the stannane (4).…”

“…156 "C/0.3 mmHg (kugelrohr) (Found: C, 79.4; H, 7.6; N, 6.3. C,,H,,NO requires C, 79.26; H, 7.54; N, 6.16%); v,,,,(neat) 1 642w, 1 454m, 916m, 824m, and 758s cm-'; m/z [EI] 227 ( M + , 16%), 210 (5), 168 (6), 136 (14), and 105 (100).…”

Siloxacyclopentenes as Dienophile-Linked Directing Groups in Intramolecular Diels−Alder Reactions

“…Synthesis of nonatrienes 5a-c began with the known Claisen rearrangement16 of commerically available 1,4-pentadien-3-ol ( 13 ) (Scheme 3). Aldehyde 14 was then treated with the lithium acetylides generated from either phenylacetylene, 2-furylacetylene or propionaldehyde acetal 16 17 to give alcohols 15a-c respectively.…”