1122-20-9Relevant academic research and scientific papers
Direct C-nitration of cyclic α,β-unsaturated oximes under the action of sodium nitrite and acetic acid in methanol
Chibiryaev,Denisov,Pyshnyi,Tkachev
, p. 1410 - 1418 (2001)
Using a number of cyclic α,β-unsaturated oximes of the terpene series and some simplest model compounds as examples, unsaturated oximes bearing a hydrogen atom at the β-carbon atom were demonstrated to be converted into β-hydroxyiminonitroalkenes under the action of sodium nitrite and acetic acid in methanol. In the case of the introduction of an alkyl substituent at the terminal carbon atom of the diene C = C-C=NOH fragment, the reaction performed under the same conditions gave rise exclusively to conjugated ketone (a deoximation product).
Mechanism of the Intramolecular Cyclization of Acetylenic Ketones
Harding, Charles E.,King, Salane L.
, p. 883 - 886 (1992)
Acid-catalyzed intramolecular cyclization of 5-cyclodecynone (1) under a variety of conditions gives bicyclo-1(6)-decen-2-one (6) as the only product.In a recent report, evidence for a reaction mechanism involving transannular triple-bond participation with a polarized carbonyl group followed by attack of the original carbonyl oxygen on the developing vinyl cation to give an unstable oxete intermediate (4) was presented.Subsequently, several workers have suggested a mechanism involving acid-catalyzed enolization of 1, followed by the transannular attack of the enol double bond at the acetylenic function, as the first two steps in an alternate process for explaining this rearrangement.When 6-octyn-2-one (9) was treated with either mineral or Lewis acids, a mixture of 1-acetyl-2-methyl-1-cyclopentene (12) and 2,3-dimethyl-2-cyclohexen-1-one (14) were produced.Experiments have shown that the oxygen atoms in the starting acetylenic ketone 9 are same ones found in the cyclic products 12 and 14.A mechanism involving cyclization of enol intermediates cannot account for the formation of 14.On the other hand, formation and rearrangement of oxete intermediates demonstrates how both 12 and 14 are produced.The results from acid-catalyzed cyclization of 6-octyn-2-one (9) are also compared to those reported for the solvolysis of the tosylate of 6-octyn-2-ol (18).
SUBSTITUTED FLUOROETHYL UREAS AS ALPHA 2 ADRENERGIC AGENTS
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Page/Page column 44; 45, (2008/12/04)
Therapeutic compounds, and methods, compositions, and medicaments related thereto are disclosed herein.
Tandem nucleophilic addition/fragmentation reactions and synthetic versatility of vinylogous acyl triflates
Kamijo, Shin,Dudley, Gregory B.
, p. 6499 - 6507 (2007/10/03)
A thorough analysis of the chemistry of vinylogous acyl triflates provides insight into important chemical processes and opens new directions in synthetic technology. Tandem nucleophilic addition/C-C bond cleaving fragmentation reactions of cyclic vinylogous acyl triflates 1 yield a variety of acyclic acetylenic compounds. Full details are disclosed herein. A wide array of nucleophiles, such as organolithium and Grignard reagents, lithium enolates and their analogues, hydride reagents, and lithium amides, are applied. The respective reactions produce ketones 2, 1,3-diketones and their analogues 3, alcohols 4, and amides 5. The present reactions are proposed to proceed through a 1,2-addition of the nucleophile to the carbonyl group of starting triflates 1 to form tetrahedral alkoxide intermediates C, followed by Grob-type fragmentation, which effects C-C bond cleavage to yield acyclic acetylenic compounds 2-5 and 7. The potent nucleofugacity of the triflate moiety is channeled through the σ-bond framework of 1, providing direct access to the fragmentation pathway without denying other typical reactions of cyclic vinylogous esters. The synthetic versatility of vinylogous acyl triflates, including functionalization reactions of the cyclic enone core (1 → 6 or 8), is also illustrated.
Selective iron-catalyzed cross-coupling reactions of Grignard reagents with enol triflates, acid chlorides, and dichloroarenes
Scheiper, Bodo,Bonnekessel, Melanie,Krause, Helga,Fuerstner, Alois
, p. 3943 - 3949 (2007/10/03)
Cheap, readily available, air stable, nontoxic, and environmentally benign iron salts such as Fe(acac)3 are excellent precatalysts for the cross-coupling of Grignard reagents with alkenyl triflates and acid chlorides. Moreover, it is shown that dichloroarene and -heteroarene derivatives as the substrates can be selectively monoalkylated by this method. All cross-coupling reactions proceed very rapidly under notably mild conditions and turned out to be compatible with a variety of functional groups in both reaction partners. A detailed analysis of the preparative results suggests that iron-catalyzed C-C bond formations can occur via different pathways. Thus, it is likely that reactions of methylmagnesium halides involve iron-ate complexes as the active components, whereas reactions of Grignard reagents with two or more carbon atoms are effected by highly reduced iron-clusters of the formal composition [Fe(MgX)2]n generated in situ. Control experiments using the ate-complex [Me4Fe]Li2 corroborate this interpretation.
(2-hydroxy)ethyl-thioureas useful as modulators of alpha2B adrenergic receptors
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, (2008/06/13)
Compounds of formula (i) and of formula (ii) wherein the symbols have the meaning disclosed in the specification, specifically or selectively modulate α2B and/or α2C adrenergic receptors in preference over α2A adrenergic receptors, and as such are useful for alleviating chronic pain and allodynia and have no or only minimal cardivascular and/or sedatory activity.
A novel tandem [2 + 2] cycloaddition-Dieckmann condensation with ynolate anions. Efficient synthesis of substituted cycloalkenones and naphthalenes via formal [n + 1] cycloaddition
Shindo,Sato,Shishido
, p. 7818 - 7824 (2007/10/03)
A novel tandem [2 + 2] cycloaddition-Dieckmann condensation via ynolate anions is described. Ynolate anions are useful for the formation of reactive β-lactone enolates via a pathway not involving the enolization of the corresponding β-lactones. The [2 + 2] cycloaddition of ynolate anions with δ- or σ-keto esters, followed by Dieckmann condensation, gives bicyclic β-lactones, which are easily decarboxylated to produce synthetically useful 2,3-disubstituted cyclopentenones and cyclohexenones in one pot. This tandem reaction was applied to a novel, one-pot synthesis of highly substituted naphthalenes.
Stereoselective benzannulations and cyclohexadienone annulations of Fischer carbene complexes in the synthesis of decala-2,4-dien-1-ones and in the synthesis of tetralin chromium tricarbonyl complexes
Hsung, Richard P.,Wulff, William D.,Challener, Cynthia A.
, p. 773 - 789 (2007/10/03)
The first general study is reported on the stereoselectivity of the benzannulation reaction involving diastereoselection at the planar center of chirality of the newly formed arene ring complexed to chromium that is induced from a chiral carbon center on the carbene complex. The stereochemistry of a number of 5- and 8-substituted tetralin chromium tricarbonyl complexes, which are produced from the benzannulations of cyclohexenyl carbene complexes with chiral centers at the 3- and 6-positions, is determined. These results are compared with the stereochemistry of the formation of 5,9- and 8,9-disubstituted decala-2,4-dien-1-ones produced from the reactions of the same carbene complexes bearing an additional substituent in the 2-position of the cyclohexenyl ring. The benzannulation reaction is most selective with 3-substituted cyclohexenyl carbene complexes giving predominately the anti-isomer of the 8-substituted tetralin chromium tricarbonyl complexes. In contrast, the cyclohexadienone annulation is most selective with 6-substituted cyclohexenyl carbene complexes giving predominately the trans-isomer of the 5,9-disubstituted decala-2,4-dien-1-ones. A mechanistic accounting of the stereochemical results is proposed which is predicated on three assumptions: 1) that the η1,η3-vinyl carbene complexed intermediate is in equilibrium, 2) vinyl ketene complex formation is irreversible and occurs with a carbon monoxide migration that is in concert with coordination of the double bond of the cyclohexene ring, and 3) the electrocyclic ring closure of the vinyl ketene complex is stereospecific.
A Stereoselective Total Synthesis of Bakkenolide-A (Fukinanolide)
Srikrishna, Adusumilli,Jagadeeswar Reddy, T.,Nagaraju, Sankuratri,Sattigeri, Jitendra A.
, p. 7841 - 7844 (2007/10/02)
A highly stereoselective synthesis of bakkenolide-A (fukinanolide, 1a) employing the radical mediated spirannulation methodology is described.
