“…In analogy with the bicyclo[3.3.0]oct-1(5)-ene system, the bicyclo[4.2.0]oct-1(6)-ene derivatives also undergo smooth ozonolysis to furnish 1,4-cyclooctanediones. Thus, 562 − 564 , readily available through [2 + 2]-photocycloaddition protocols, on oxidative cleavage with ozone furnished 565 , 566 ,240a and 567 ,240b respectively, representing various domains of the taxoid framework, Scheme . 116 …”
Section: Reductive and Oxidative Processesmentioning
“…In analogy with the bicyclo[3.3.0]oct-1(5)-ene system, the bicyclo[4.2.0]oct-1(6)-ene derivatives also undergo smooth ozonolysis to furnish 1,4-cyclooctanediones. Thus, 562 − 564 , readily available through [2 + 2]-photocycloaddition protocols, on oxidative cleavage with ozone furnished 565 , 566 ,240a and 567 ,240b respectively, representing various domains of the taxoid framework, Scheme . 116 …”
Section: Reductive and Oxidative Processesmentioning
A route to bicyclo[n.3.0] ring systems (n = 5-7) has been devised. Key transformations include an intermolecular diyl trapping reaction (1 + 3 --> 4), and fragmentation of the resulting tricyclic cycloadduct 4 (4 --> 5). A variety of diylophiles were examined, including electron deficient (6, 7, 21, 29, 30, 31), electron rich (8), and push-pull cycloalkenes (9, 10, 19, 20).
“…However, the phenanthrenone isomer of 18 is likely to be favored thermodynamically over its bridged counterpart: While conformation III (Figure ) would be highly destabilized by a peri interaction with the C1 methyl group, conformation IV is not affected by the methyl group at C1. The [6.4.0]bicyclododecane ring is present in numerous natural product classes including the neolemnane family of sesquiterpenoids and the taxanes. − Ozonolysis of the double bond of compounds such as 19 would, in principle, produce highly functionalized synthons to compounds containing the ubiquitous [6.4.0] bicyclododecane ring system. 2 …”
A series of Michael acceptors has been combined with the Os(II) eta(2)-naphthalene complex (1) to form stable 1H-naphthalenium species. Under acidic conditions, these complexes undergo ring closure at C2 to form the phenanthrenone core. In contrast, the corresponding 1-methylnaphthalene complex (15) upon addition of MVK at C8 undergoes ring closure at C5 to form a bridged tricyclic complex (18). Michael addition of MVK to the naphthalene complex (1) followed by deprotonation, an inter-ring linkage isomerization, and ring closure forms a 9-methylphenalene complex (21). In all cases, the organic cyclization products may be decomplexed by heating with silver triflate and isolated in moderate yield.
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