Cyclopentenone synthesis

KHAND PAUSON Cyclopentenone Annulat/on Cyclopentenone synthesis from cartxin monoxide acetylene and olefins, cobalt carbonyl catalyzed. 

NAZAROV Cyclopentenone synthesis Acid catalyzed cyclaation of dienones to cyclopentenones... 

Continuous cyclopentenone synthesis with static mixer reactor... 

Castagnino, E., Corsano, S., and Strappavecchia, G.P., The preparation of a novel oxo-cyclopenten-2-phosphonate derivative, useful intermediate for 2-alkyl-substituted cyclopentenones synthesis, Tetrahedron Lett., 93, 1985. 

Ellison RA, Lukenbach ER, Chiu C-W (1975) Cyclopentenone synthesis by aldol condensation. Synthesis of a key prostaglandin intermediate. Tetrahedron Lett 16 499-502... 

Cyclopentenones. One limitation to Jung s cyclopentenone synthesis (8, 178) is that telrasubstituted alkcncs react slowly, if at all, with this diene (I). An expedient in the use of a dienophile such as isobutenyl acetate (2), which does react, even if slowly, to give 3 as the major adduct. The adduct can be converted in several steps lo a cyclopcntcnonc such as 4. The cyclopentenone 4 (R = p-tolyl) has been converted to /(-cuparcnonc (5).2... 

Cyclopentenone synthesis.2 The key step in a regiospecific synthesis of methylenemycin B (4) involves the reaction of (2-butyne)hexacarbonyldicobalt (1) with tetrahydro-2-(2-propenyloxy)pyrane (2). Although the reaction of complexes... 

Three-component reactions involving zirconocyclopentadienes have been also employed in cyclopentenone synthesis. The method combines disubstituted alkynes, isocyanates, and arylidene or alkylidene malononitriles to assemble polysubstituted cyclopentenones 171 (Scheme 8.77) [160],... 

Interestingly, zirconacyclopentane 246 formed by the reaction of 1,6-heptadiene with the Zr complex has the firms ring junction mainly [108]. It should be noted that the preparation of the trans ring junction in the bicyclo[3.3.0]octane system by other means is difficult. Carbonylation of 246 affords trans-fuzed bicyclo[3.3.0]octanone 247 [109,111]. The diacetoxy compound 248 is obtained by oxidative cleavage of 246. Protonation affords the frans-dimethylcyclopentane skeleton. Similar reactions occur with 1,6-enynes, and Pauson Khand-type cyclopentenone synthesis is possible by carbonylation. 

In an unconventional cyclopentenone synthesis, Negishi cyclised vinyllithiums derived from the 1-iodo- 1-silyl alkenes 103 onto preformed lithium carboxylate salts.57 He later found58 that amides 104 function in this reaction rather better than the carboxylate salts, and that the silyl substituent is not necessary for cyclisation. Nitriles, on the other hand, fail to cyclise. 

Access to (Z)-vinyl bromides allowed an efficient cyclopentenone synthesis and their application to the formation of cyclopentanoid natural products such as rosaprostol or a selective cox-2 inhibitor [63] (Eq. 47). 

In a mechanistically quite different process Ni(CO>4 is the catalyst precursor and the double bond of an allylic halide serves as the alkene component in another cyclopentenone synthesis. Sequential insertion of the alkyne and CO into an initially formed allyl-Ni complex leads to the primary cyclization product, a (2-oxo-3-cyclopenten-l-yl)methylnickel complex (Scheme 4). The final product of the sequence depends on which of several possible reactions of the latter take place. Important features of this reaction have been described in several reviews. " ... 

The opening of halocyclopropanes to allyl systems according to equation 124 can happen thermally or with the assistance of electrophiles and nucleophiles . Some recent examples include an efficient cyclopentenone synthesis (equation 125) ", an electrocyclic opening/cyclization sequence giving functionalized furan and pyran derivatives (equation 126), an elegant total synthesis of the very fast death factor alkaloid ( ) anatoxin and a nice application of the well known nucleophilic opening to the preparation of crystalline methylene aziridines (equation 127) . 

Annelation of a three-carbon unit derived from cyclopropenone acetals across the sp carbon atoms of electron-deficient olefins has provided a simple new cyclopentenone synthesis Thus, a 1 1 mixture of the a,j5-unsaturated ketone 275 and acetal 276 affords... 

Pauson-Khand reactions. This salt Na[CpMo(CO)3] converts alkyne-dicobalthexacarbonyl complexes into mixed Co-Mo analogs which often show higher reactivities in the cyclopentenone synthesis. 

Cyclopentenone synthesis.2 The reaction of a,a -dibromoketones with enamines in the presence of diiron nonacarbonyl gives cyclopentenone derivatives in 50-100 % yield. Thus the reaction of (1) with a-morpholinostyrene (2) with diiron nonacarbonyl as reducing agent gives the cyclopentenone (3) in 94% yield. 

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