- Pd(II)-Catalyzed Enantioselective Desymmetrization of Polycyclic Cyclohexenediones: Conjugate Addition versus Oxidative Heck
-
Pd(II)-catalyzed desymmetrization of polycyclic cyclohexenediones has been achieved with high enantio- and diastereoselectivities. Up to five contiguous stereocenters are desymmetrized, while simultaneously, an additional stereocenter is created by the enantioselective conjugate addition. Surprisingly, the conjugate addition products dominate even under typical oxidative Heck conditions, and these observations may provide some insight into the competition between the two related reactions.
- Lamb, Claire J. C.,Vilela, Filipe,Lee, Ai-Lan
-
p. 8689 - 8694
(2019/11/03)
-
- High-efficiency microphotooxidation using milliwatt LED sources
-
Inexpensive milliwatt light emitting diode (LED) sources allow energy- and atom-efficient microphotochemical reactions. Thus, sources constructed from three 120 mW 5 mm diameter 627 nm LED's enable μmol-mmol scale methylene blue-sensitized singlet oxygen photooxidations of various arenes and cyclopentadienones using a 3-5 M excess of oxygen in 82-98% yields.
- Carney, John M.,Hammer, Reagan J.,Hulce, Martin,Lomas, Chad M.,Miyashiro, Dayna
-
experimental part
p. 352 - 355
(2011/02/28)
-
- Facile multistep synthesis of isotruxene and isotruxenone
-
(Chemical Equation Presented) Three multistep approaches toward facile syntheses of isotruxene (1) and isotruxenone (3) are reported. The ortho-para conjugated backbone in the precursor 4 was constructed by either Co-catalyzed [2 + 2 + 2] cyclotrimerization or the [4 + 2] Diels-Alder reactions. The regioselectivity of the triple intramolecular Friedel-Crafts acylation of 4 plays the key role in determining the overall yield. Compared to the previous one-step method, the current approaches are more efficient in terms of product yield (27-36% vs 4-18%) and purification (i.e., free of column chromatography).
- Yang, Jye-Shane,Huang, Hsin-Hau,Lin, Shih-Hsun
-
supporting information; experimental part
p. 3974 - 3977
(2009/10/14)
-
- Steric Effects in the Dimerization of 2,5-Dialkyl-3,4-Diphenylcyclopentadienones
-
Some novel methyl- and ethyl-substituted dimers of 2,4-diphenylcyclopentadienones have been detected.Their enthalpies of dimerization have been determined and compared with values calculated by molecular mechanics.The steric demands of this dimerization have thus been clarified.
- Weiss, Hilton M.
-
p. 439 - 443
(2007/10/02)
-
- Synthesis of Some New Polynuclear Compounds by Cycloaddition Reaction
-
A large number of 7,9-disubstituted derivatives (I) of cyclopentacenaphthylene-8(H)-one and 2,5-disubstituted derivatives (II) of 3,4-diphenylcyclopentadienone have been synthesized by condensing acenaphthaquinone and benzil separately with suitable 1,3-disubstituted propan-2-ones.The 3-(o- and p-methoxytolyl)cyclopentadienones (IX) have been synthesized by Friedel-Crafts reaction of appropriate methyl cresyl ethers and phenacyl chloride.These dienones have been subjected to Diels-Alder reaction with acenaphthylene and a new acetylenic dienophile (V) (whose synthesis is also described in this paper) to yield a large number of polynuclear aromatic compounds having fluoranthene and p-quaterphenyl nuclei, which have been finally characterised by elemental analyses, IR and PMR spectral data.
- Samanta, S. R.,Mukherjee, A. K.
-
-
- 1,2-Diphenyl-3,5-dimethyl-4-oxo-6,7-diazabicyclohept-2-ene, a nitrogen unsubstituted diazetidine with an unusually unreactive nitrogen.
-
In the title ring system, the benzylic nitrogen (N7), whether substituted or not, is abnormally unreactive.Hydrolysis of the di-urethanes 3a or b occurs readily at N6 to give 10a or b, but not at all at N7.In 3d Pd-H2 remo
- McIntyre, Deane D.,MacKay, Donald,Wong, Lichin L.
-
p. 1316 - 1323
(2007/10/02)
-
- PHOTOCHEMICAL STUDIES. IRRADIATION INDUCED TRANSFORMATIONS OF REVERSIBLY DISSOCIATING CYCLOPENTADIENONE-DIMERS AND THEIR MONOMERS
-
Irradiation of dissociating cyclopentadienone-dimers (2b,c,e) results in formation of two types of cage-products (5 and 8) in very low quatum yields and good, but vawelength and phase dependent chemical yields.Both processes are intramolecular; for 2b thi
- Fuchs, Benzion,Pasternak, Mordechai,Pazhenchevsky, Barak
-
p. 3443 - 3452
(2007/10/02)
-