70079-75-3Relevant articles and documents
Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
supporting information, p. 8135 - 8148 (2019/05/29)
The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)-italicene.
Evidence for Triplet Sensitization in the Visible-Light-Induced [2+2] Photocycloaddition of Eniminium Ions
H?rmann, Fabian M.,Chung, Tim S.,Rodriguez, Elsa,Jakob, Matthias,Bach, Thorsten
, p. 827 - 831 (2017/12/26)
Εniminium ions were prepared from the corresponding α,β-unsaturated carbonyl compounds (enones and enals), and were found to be promoted to their respective triplet states by energy transfer. The photoexcited intermediates underwent intra- or intermolecular [2+2] photocycloaddition in good yields (50–78 %) upon irradiation at λ=433 nm or λ=457 nm. Iridium or ruthenium complexes with a sufficiently high triplet energy were identified as efficient catalysts (2.5 mol % catalyst loading) for the reaction. The intermolecular [2+2] photocycloaddition of an eniminium ion derived from a chiral secondary amine proceeded with high enantioselectivity (88 % ee).
Br?nsted Acid Catalysis in Visible-Light-Induced [2+2] Photocycloaddition Reactions of Enone Dithianes
Brenninger, Christoph,P?thig, Alexander,Bach, Thorsten
supporting information, p. 4337 - 4341 (2017/04/04)
1,3-Dithiane-protected enones (enone dithianes) were found to undergo an intramolecular [2+2] photocycloaddition under visible-light irradiation (λ=405 nm) in the presence of a Br?nsted acid (7.5–10 mol %). Key to the success of the reaction is presumably the formation of colored thionium ions, which are intermediates of the catalytic cycle. Cyclobutanes were thus obtained in very good yields (78–90 %). It is also shown that the dithiane moiety can be reductively or oxidatively removed without affecting the photochemically constructed ring skeleton.
Intramolecular azide-alkene 1,3-dipolar cycloaddition/enamine addition(s) cascade reaction: Synthesis of nitrogen-containing heterocycles
De Miguel, Irene,Herradon, Bernardo,Mann, Enrique
supporting information; experimental part, p. 1731 - 1736 (2012/07/28)
A cascade intramolecular azide-alkene 1,3-dipolar cycloaddition/1,2 enamine and/or 1,4 enamine addition reaction sequence has been developed, and provides access to a variety of nitrogen containing heterocycles from readily available ω-azido alkenes. Copy
Copper-catalyzed asymmetric conjugate addition of trialkylaluminium reagents to trisubstituted enones: Construction of chiral quaternary centers
Vuagnoux-D'Augustin, Magali,Alexakis, Alexandre
, p. 9647 - 9662 (2008/12/21)
Me3Al, Et1Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3-CN)4]BF4 or [CuOTf]2· C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions.
Enantioselective copper-catalyzed conjugate addition to trisubstituted cyclohexenones: Construction of stereogenic quaternary centers
D'Augustin, Magali,Palais, Laeticia,Alexakis, Alexandre
, p. 1376 - 1378 (2007/10/03)
Trimethyl- and triethylaluminum undergo enantioselective conjugate addition to 3-and 2-substituted cyclohexenones in the presence of catalytic amounts of a Cu salt and a phosphoramidite ligand L* (see scheme). Thus, chiral quaternary centers can be built with up to 96.6% ee. Functionalized enones lead to bicyclic structures by a subsequent aldol reaction.
Synthesis and biological activity of 22-oxa CD-ring modified analogues of 1α,25-dihydroxyvitamin D3: Spiro[5.5]undecane CF-ring analogues
Schepens, Wim,Van Haver, Dirk,Vandewalle, Maurits,De Clercq, Pierre J.,Bouillon, Roger,Verstuyf, Annemieke
, p. 3889 - 3892 (2007/10/03)
The synthesis and biological activity of novel CD-ring modified analogues of 22-oxa-1α,25-dihydroxyvitamin D3, lacking the D-ring and featuring a connection between C-18 and C-21 (spiro[5.5]undecane CF-ring analogues), is described. The central
Asymmetric spirocyclization: A new type of acid-catalyzed intramolecular 1,4-addition to form carba-spirocyclic compounds
Yamada, Satoshi,Karasawa, Satoru,Takahashi, Youichi,Aso, Mariko,Suemune, Hiroshi
, p. 15555 - 15566 (2007/10/03)
Novel spirocyclization based on intramolecular 1,4-addition and its asymmetric version have been developed using a combination of Lewis acid and 1,2-diol. Treatment of five- and six-membered α,β-unsaturated cyclic ketones having a 4-oxopentyl group at the
Photoreactions of Enones with Amines - Cyclization of Unsaturated Enones and Reductive Ring Opening by Photoinduced Electron Transfer (PET)
Mattay, Jochen,Banning, Anja,Bischof, Eric W.,Heidbreder, Andreas,Runsink, Jan
, p. 2119 - 2128 (2007/10/02)
Photolysis of the unsaturated enones 1 yields cycloaddition products 2 and 3 with varying regioselectivity.Under electron transfer conditions (PET) spirocyclic products 4 are formed.The straight cycloaddition products 2b, c, f are converted to the spirocyclic products 4b, c, f under the same reaction conditions.The cyclobutane 5 and cyclopropane 11 also undergo this new reductive ring opening reaction, while the stabilized system 7 is converted to reduced ring-enlarged triquinane 10 which may be interesting in natural product synthesis. - Irradiation of 2-cyclohexen-1-one (14) in the presence of N,N-dimethylallylamine (15) leads to the decahydroisoquinoline 18.A mechanism involving radical intermediates is discussed. Key Words: Photoinduced electron transfer / Cyclization / Ring opening / Enones
