Cyclopentannulations leading to the synthesis of bicyclic conjugated enediones.

Yechezkel, Tamar; Ghera, Eugene; Ostercamp, Daryl L.; Häßner, Alfred

doi:10.1021/jo00121a035

Cited by 40 publications

(21 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Compounds 22 and 23 contain the nucleus present in the pyrrolizidine alkaloids. Many pyrrolizidine derivatives are known, 13 but few with a carbonyl group in the 2 position of the rings as in 22 and 23 have been documented. However, the reduction of oximes 24a-f under these conditions gave only bicyclic compounds 26a-f and 27a-f, obtained as single diastereomers (Table 1), while hydrogenation using W7 Raney nickel produced only amines 25 (as 1:1 mixtures of diastereomers) which upon acetylation formed 28d-f.…”

mentioning

confidence: 99%

The chemistry of enaminones, diazocarbonyls and small rings: our contribution

Kascheres¹

2003

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

mentioning

confidence: 99%

The chemistry of enaminones, diazocarbonyls and small rings: our contribution

Kascheres¹

2003

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

“…On the other hand, it is well known that alkyl sulfoxides bearing a hydrogen at the b-carbon atom undergo thermal decomposition to form unsaturated compounds. 15 Having this in mind, we decided to investigate the reaction between easily available 2-(phenylsulfinyl)cyclopent-2-enone 16 with diethyl lithiomethylphosphonate as a key step in the synthesis of the title compounds. In fact, treatment of the above cyclopentenone sulfoxide with Li-3 at -78°C in tetrahydrofuran gave the expected 1,4-adduct 6a, which was obtained in 40% yield after purification by column chromatography.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of 3-(Phosphorylmethyl)cycloalkenones by Forced Conjugate Addition of α-Phosphonate Carbanions to Cyclic Enones

Mikołajczyk¹,

Perlikowska²

2007

Synthesis

View full text Add to dashboard Cite

Cycloalkenones were found to react with a-lithiated diethyl (phenylselanyl)methylphosphonate preferentially or exclusively at the carbonyl group giving 1,2-adducts. When complexes of cycloalkenones with aluminum tris(2,6-diphenylphenoxide) were used for this reaction, regioselective 1,4-addition was observed. Upon oxidation the thus-formed 1,4-adducts gave the corresponding 3-(phosphorylmethyl)cycloalk-2-enones. An alternative approach to the latter compounds involved 1,4-addition of diethyl lithiomethylphosphonate to 2-sulfinylcycloalk-2-enones followed by sulfoxide elimination.Cycloalkenones are valuable intermediates in a variety of synthetic transformations and useful building blocks in the synthesis of biologically active compounds. Among them, cyclopentenones are particularly interesting due to the presence of this structural motif in a wide range of important natural products, such as jasmonoids, cyclopentanoid antibiotics, and prostanoids. As part of our broad program on the application of phosphorus and sulfur reagents in organic synthesis, 1 we have also been engaged in the invention and development of general methods for the synthesis of functionalized cyclopentenones and cyclopentanones. 2 These endeavors resulted in the elaboration of new and efficient routes to racemic rosaprostol 3 and enantiomeric prostaglandin B 1 methyl esters 4 starting from 3-[(dimethoxyphosphoryl)methyl]cyclopent-2-enone (1a¢) as a key intermediate and to both enantiomers of isoterrein 5 and neplanocin A 6 from the diastereomeric camphor protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enones 2a and 2b.The starting cyclopentenones 1 and 2 (Figure 1) have been obtained by general methods for the synthesis of 3-(phosphorylmethyl)cycloalk-2-enones developed in our laboratory involving the reaction of dicarboxylic acid esters with a-phosphonate carbanions and subsequent intramolecular Horner reaction of bis(b-oxophosphonates), which were formed in the initial step. 7 This method complemented two other approaches to 3-(phosphorylmethyl)cycloalk-2-enones. The first employed oxidation of cyclic allylic alcohols obtained in the carbonyl addition of a-phosphonate anions to cycloalkenones, 8 while the second was based on substitution of the b-methoxy group in cyclic enones by a-lithiated alkylphosphonates. 9

show abstract

“…The column was an analytical Waters µPorasil (3.9 mm ϫ 300 mm), the flow was 1.3 mL/min with a hexane/ethyl acetate mixture (80:20, HPLC-grade) as eluent. The substrates, [14] NsONHCO 2 -Et, [15] NsONHCO 2 tBu [16] and TsONHCO 2 tBu [17] were synthesised as reported in the literature. IR: PerkinϪElmer 1600 series FTIR spectrophotometer.…”

Section: Methodsmentioning

confidence: 99%