Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Six-membered-ring carbocyclics

Dipolar cycloaddUions. Interest in 1,3-dipolar cycloadditions increased dramatically during the past 20 years, largely because of the pioneering studies of Huisgen [7, 2] The versatility of this class of pericychc reactions in the synthesis of five-membered-ring heterocyclic compounds is comparable with that of the Diels-Alder reaction in the synthesis of six-membered-ring carbocyclic systems (equation 1)... [Pg.797]

The formation of six-membered ring carbocycles is illustrated in Scheme 39 [132, 133]. The reaction proceeds well with aryl bromides, iodides, and triflates especially when containing additional electron-withdrawing groups, while aryl chlorides are converted in low yields only. It has been demonstrated, that for less reactive p-methoxyaryl derivatives the addition of lithium iodide improves the results significantly [132]. [Pg.71]

W. G. Bentrude Conformational Studies of Six-Membered Ring Carbocycles and Heterocycles Ed. E. Juaristi, Publ. JCH 1995 pp 245-293. [Pg.355]

There is no equilibrium between 2 and 3 under the reaction conditions employed. However, the generation of palladium hydride (H-Pd) from adventitious water and syn addition of H-Pd to the alkyne portion is highly likely to initiate the six-membered ring carbocyclization. Thus, cyclizations in the presence of an excess amount (600 mol%) of deuterated water (D2O) were examined [51,52]. Indeed, the products D-2a and D-3a, which were regiospecif-ically deuterated at the exo olefin in the a position to the ester functionality, were obtained with -75% deuterium content (Scheme 8). [Pg.286]

Alkynic aldehydes likewise undergo intramolecular coupling to generate five- and six-membered ring carbocycles. This protocol has been utilized as a key step in the synthesis of isocarbacyclin (eq TA) Sml2 was found to be superior to several other reagents in this conversion. [Pg.380]

A number of research groups have used ring-closing metathesis to prepare conformationally constrained a- and P-amino acids containing six-membered ring carbocycles. Several key examples are discussed in the paragraphs below. [Pg.512]

Clive and Liu used a ring-closing metathesis strategy to access the six-member ring carbocyclic components of the anticancer agent s ottelione A and Olefin metathesis of 158 or 160 with catalytic amount of 3 in the presence of dichloromethane provided the corresponding carbocycles 159 and 161 in 93 and 86% yields, respectively. The authors also attempted this... [Pg.517]

Aggarawa and co-workers applied their strategy for the synthesis of five- and six- membered ring carbocyclic silyl enol ethers to the the synthesis of seven-membered ring carbocyclic silyl enol ether bearing a phenyl substituent. Substrate 230 required upward of 20 mol % of 4 in refluxing benzene to achieve modest yields of the desired product 231. [Pg.530]

Miscellaneous Gold- and Iron-Catalyzed Cascade Reactions The car-benic reactivity of gold catalysis was exploited toward the synthesis of stereoselective six-membered ring carbocycles, through cyclopropanation reactions incorporated in cascade sequences [31]. [Pg.194]

Carbocyclic molecules occupy a special position in stereochemistry. While Barton s proposal (80) triggered explosive developments in the conformational analysis of six-membered ring compounds (80a), the inability of the qualitative theory to interpret the behavior of rings other than six membered prompted Hendrickson to utilize the MM method (9b). Further developments in this area have been well summarized (10, 81). Some of the more recent topics are mentioned below. [Pg.129]

Another tetracyclic carbon skeleton, named cumbiane, has been isolated from Pseudopterogorgia elisahethae. Its representatives are the diterpenoids cumbiasin A (33) and B (34) [20] their structures and relative configurations were elucidated by interpretation of a combination of spectral data. The six-membered ring D was formed by connecting CIO and C16 of an elisabethane carbon skeleton. The carbocyclic skeleton of the cumbiasins is unprecedented and represents a new class of C20 rearranged diterpenes. The tricyclic seco-cumbiane skeleton is derived from the cumbiasins by cleavage of the C15-C16 bond. Due to intramolecular cyclizations two additional oxo-heterocycles are present in cumbiasin C (35) [20] (Fig. 7). [Pg.12]

Analogously to the carbocycle and oxycycle synthesis, cyclic amines can be obtained by the hydrosilylation of a suitable enyne, such as 46 (Reaction 7.54), which gave the six-membered ring via a 6-endo cyclization of the vinyl radical onto the C=N bond [63]. In another example, the isothiocyanide functionality of compounds 47 or 48 reacts with silane under radical conditions... [Pg.164]

Tricyclic Systems Central Carbocyclic Ring with Fused Five- and Six-membered Rings... [Pg.1201]


See other pages where Six-membered-ring carbocyclics is mentioned: [Pg.332]    [Pg.495]    [Pg.509]    [Pg.509]    [Pg.521]    [Pg.451]    [Pg.391]    [Pg.192]    [Pg.332]    [Pg.495]    [Pg.509]    [Pg.509]    [Pg.521]    [Pg.451]    [Pg.391]    [Pg.192]    [Pg.3]    [Pg.154]    [Pg.115]    [Pg.720]    [Pg.187]    [Pg.92]    [Pg.269]    [Pg.358]    [Pg.81]    [Pg.148]    [Pg.255]    [Pg.460]    [Pg.107]    [Pg.215]    [Pg.741]    [Pg.498]   
See also in sourсe #XX -- [ Pg.339 ]




SEARCH



Rings six-member

Six-membered carbocycle

Six-membered carbocycles

© 2024 chempedia.info