Organoiron complexes in organic synthesis. Part 6. Dienolonium equivalents: tricarbonyl-[1-alkoxy-2-(1–5-η-4-methoxycyclohexa-2,4dienylium)ethane]iron hexafluorophosphates and related complexes leading to masked 4,4-disubstituted cyclohexenones

Tricarbonyl[(1−4-η)-2-Methoxy-5-methylenecyclohexa- 1,3-diene]iron as a Synthetic Intermediate: Sequential Electrophilic and Nucleophilic Additions

“…The reaction of the salt with the potassium enolate of dimethyl malonate took place stereoselectively to give complex 3b in high yield. Reaction of this salt with the potassium enolate of dimethyl malonate has been reported to give both C-1 (major) and C-5 (minor) addition products. , In this case, the minor C-5 adduct may have been lost during the workup and purification processes. The overall sequence of electrophilic−nucleophilic addition reactions should lead to a useful methodology for organic synthesis (Table ).…”

Quinolines spiro annulated at heterocyclic fragment: Synthesis and properties

“…All known synthetic attempts to build this heterocyclic core start from amine precursors where the spiro annulation process into the spiro[cyclohexadiene- Reaction of p-anisidine and complex salt 94 (obtained from p-methoxyphenylacetic acid in four step procedure [120]) in acetonitrile at reflux led regio-diastereoselectively in 80% yield to the 2,3-dihydrodimethoxy spiro-4(1H)quinoline 95 involving a sequence of electrophilic substitution of p-anisidine and in situ nucleophilic substitution of the leaving group in the side chain. Spiro-4(1H)quinoline 95 was converted into the free ligand 96 through the demetalation with trimethylamine N-oxide as outlined in Scheme 39 [121,122].…”

Synthetic applications of cationic iron and cobalt carbonyl complexes

“…Examples of nucleophiles that have been used are heteroatom nucleophiles such as alkoxides, 16 amines, 19 phosphines 20 and phosphites, 21 but also various carbon nucleophiles. The latter class includes electron rich aromatics, 22 malonates, 23 silyl enol ethers, 24 tin enolates, 25 enamines, 26 amides, 27 allyl silanes, 28 nitromethane anion, 29 cyanide, 30 and various highly activated carbon species such as dialkyl cadmium 31 and dialkyl zinc reagents. 32 Grignard reagents and alkyl lithiums can be problematic as in some cases a radical-mediated dimerization reaction occurs as a side reaction.…”