21889-88-3Relevant articles and documents
Solvent, counterion, and secondary deuterium kinetic isotope effects in the anionic oxy-Cope rearrangement
Gajewski, Joseph J.,Gee, Kyle R.
, p. 967 - 971 (1991)
The potassium and sodium alkoxides of 3-methyl-1,5-hexadien-3-ol follow first-order kinetics in the process of undergoing the anionic oxy-Cope rearrangement in tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO). The first-order rate constant for the rearrangement of the potassium alkoxide in DMSO is ca. 1000 times faster than that in THF, as is the first-order rate constant in THF in the presence of 1 equiv or excess 18-crown-6. The rate constants in THF are independent of initial alkoxide concentration; in contrast, the first-order rate constants in DMSO are inversely proportional to the initial alkoxide concentration, and addition of potassium salts to the DMSO solution results in a retardation of rearrangement rate. Addition of 1/4 and 1/2 equiv of 18-crown-6 in THF gave first-order behavior only over the first 25% of reaction with an initial rate constant linearly related to that with 1 equiv of crown ether. Secondary deuterium kinetic isotope effects have been determined at the bond-breaking and bond-making sites in the Cope rearrangement of the potassium alkoxide in THF, in THF in the presence of 18-crown-6, and in DMSO. The isotope effects indicate a highly dissociative transition state with substantial bond breaking of the C3-C4 bond and little bond making between the allylic termini (C1 and C6). The effects of aggregation and ionic dissociation are discussed in the context of mechanistic pathways proposed for the rearrangement in THF and in DMSO.
Iron-Catalyzed Synthesis of α-Dienyl Five- and Six-Membered N-Heterocycles
Gonnard, Laurine,Guérinot, Amandine,Cossy, Janine
supporting information, p. 6160 - 6167 (2017/11/15)
The iron-catalyzed synthesis of α-dienyl N-heterocycles is reported. The method is cost-effective, atom-economic, and led to a range of substituted α-dienyl heterocycles in moderate to good yields and diastereoselectivities. The α-dienyl piperidines are key synthetic intermediates as demonstrated by the preparation of a panel of α-polyenyl N-heterocycles.
Synthesis of 3D-Rich Heterocycles: Hexahydropyrazolo[1,5-A]pyridin-2(1H)-ones and Octahydro-2H-2a,2a1-diazacyclopenta[cd]inden-2-ones
Pu?avec Kirar, Eva,Drev, Miha,Mirnik, Jona,Gro?elj, Uro?,Golobi?, Amalija,Dahmann, Georg,Po?gan, Franc,?tefane, Bogdan,Svete, Jurij
, p. 8920 - 8933 (2016/10/14)
Two cyclic azomethine imines, 7-methyl- and 7-phenyl-2-oxo-Δ7-hexahydropyrazolo[1,5-A]pyridin-8-ium-1-ide, were prepared in seven steps from the respective commercially available δ-keto acids. The addition of Grignard reagents followed by N-Alkylation at position 1 afforded the 1,7,7-trisubstituted hexahydropyrazolo[1,5-A]pyridin-2(1H)-ones, whereas 1,3-dipolar cycloadditions of these dipoles to typical acetylenic and olefinic dipolarophiles gave 4a-substituted 2a,2a1-diazacyclopenta[cd]indene derivatives as the first representatives of a novel heterocyclic system. Regio- and stereoselectivity as well as the mechanism of these [3 + 2]-cycloadditions were evaluated using computational and experimental methods. The data obtained were in agreement with the polar concerted cycloaddition mechanism via the energetically favorable syn/endo-transition states.
