938-06-7Relevant academic research and scientific papers
Stereospecific Photoreduction of Polycyclic α,β-Unsaturated Ketones
Chan, Alexander C.,Schuster, David I.
, p. 4561 - 4567 (1986)
The photolysis of 4a-methyl-4,4a,9,10-tetrahydro-2(3H)-phenenthrone (1) in isopropyl alcohol (i-PrOH) is found to give lumikeone rearrangement product 5 and reduction product 8 via the enone triplet ?,?* excited state.Other reduction products 6,7, and 9, arise from the triplet n,?* excited state.The lower limit of the energy of the triplet state En,?* is estimated to be ca. 67 kcal/mol above the ground state and that of the relaxed triplet ?,?* excited state is ca. 61 kcal/mol.Reduction of the C=C bond on the enone chromophore from both excited states is stereospecific, with the twisted ?,?* triplet leading exclusively to cis-fused bicyclic ketone and the planar n,?* triplet to the trans fused isomer.The results from the photolysis of 4a-methyl-4,4a,5,6,7,8-hexahydro-2(3H)-naphthalenone (4) are consistent with these findings.
High trans-2-Decalones by Photoredox Catalyzed β-Isomerization
Sombret, Juliette,Quintaine, Julie,Biremond, Tony,Barnes, Quentin,de Saint-Laumer, Jean-Yves,Saudan, Lionel
, (2021/12/03)
The synergistic combination of three catalytic processes – photoredox, enamine and hydrogen atom transfer (HAT) catalysis – enabled the β-isomerization of 2-decalones towards the thermodynamically most stable trans-isomers. A library of iridium (III) complexes and organic dyes were screened in combination with cyclic amines and thiols which after optimization gave the desired trans-2-decalones with high trans/cis ratios of 60 : 40 up to 98 : 2.
[4 + 3] cycloadditions of cyclic oxyallyls and cyclic 1,3-dienes
Jin, Shu-Juan,Choi, Jong-Ryoo,Oh, Jonghoon,Lee, Dongha,Cha, Jin Kun
, p. 10914 - 10921 (2007/10/03)
The [4 + 3] cycloaddition of the oxyallyl intermediates, derived from 2-chlorocyclohexanone and related compounds, to cyclic 1,3-dienes under the F?hlisch conditions (Et3N in CF3CH2OH) has been examined to assess its scope
Palladium Assisted Transfer Hydrogenation of Cyclic α,β-Unsaturated Ketones by Ammonium Formate
Rao, H. Surya Prakash,Reddy, K. Subba
, p. 171 - 174 (2007/10/02)
α,β-Unsaturated ketones can be hydrogenated conveniently under catalytic hydrogenation conditions using ammonium formate / Pd-C (10percent) in refluxing methanol.
Equilibration of Alkene Regioisomers in trans- and cis-Octalins
Thompson, Hugh W.,Gaglani, Kamlesh D.
, p. 967 - 972 (2007/10/02)
As models for studying the energetics of double-bond regiochemistry in the octalin system, the enol acetates of trans- and cis-2-decalone (1,4), trans- and cis-10-methyl-2-decalone (7,10) and trans- and cis-9-methyl-2-decalone (13,16) have been synthesized.Acid-catalyzed equilibrations of double-bond position were conducted in acetic anhydride at ca. 60, 100 and 140 deg C and assessed by integration of the vinyl-proton NMR signals, which were unambiguously assigned to each enol acetate either by the observed splitting pattern or synthesis.Values of ΔH and ΔS (Δ2:Δ1) are derived and compared with experimental and theoretical literature values.Values of ΔH for the enol acetates of 1 and 4 are -0.69 and 0.0 kcal mol-1, respectively, and addition of an angular methyl decreases the relative stability (ΔH) of the Δ1 isomer, by 1.25 - 2.25 kcal mol-1 for the trans skeleton and by 1.0 - 1.4 kcal mol-1 for the cis skeleton.For a given angular substituent, changing cis stereochemistry to trans also decreases the relative Δ1-stability, by 0.7 kcal mol-1 when R = H and 0.95 - 1.55 kcal mol-1 when R = Me.Values of ΔS are all small, between +0.1 and -3.2 cal mol-1 K-1.Trends in the data and features of the 1H NMR spectra related to conformation are discussed, and an approach is suggested for calculating approximate ΔH, ΔS and ΔG values for Δ1-9-methyl- vs. Δ1-10-methyloctalin in the trans and cis series.
SELECTIVITE DE LA REDUCTION D'α-ENONES POLYCYCLIQUES PAR LES BOROHYDRURES: EFFET DE L'ADDITION DE TETRAMETHYL-ETHYLENEDIAMINE AU BOROHYDRURE DE TETRABUTYLAMMONIUM
D'incan, E.,Loupy, A.,Maia, A.,Seyden-Penne, J.,Viout, P.
, p. 2923 - 2927 (2007/10/02)
Δ1,9octalone, Δ1,9-10-methyl octalone and testosterone were reduced by NBu4BH4, alone or in the presence of tetramethylethylenediamine (TMEDA), in THF and in toluene.With TMEDA, the first step of the reduction is the regioselective 1,4 attack by BH4(1-) which leads either to the saturated ketones or to the corresponding saturated alcohols.The results observed under different conditions were interpreted by the intervention of various reductive species: diborane, enoxyborohydrides in the absence of TMEDA, amine-borane in its presence.
Dienone-Phenol Rearrangements of Bicyclic Cyclohexa-2,5-dienones; Confirmation of a Multistage Mechanism
Waring, Anthony J.,Zaidi, Javid Hussain,Pilkington, James W.
, p. 1454 - 1459 (2007/10/02)
Two mechanisms are well established for the dienone-phenol rearrangements of bicyclic cyclohexadienones of the 4a-alkyl-5,6,7,8-tetrahydronaphthalen-2(4aH)-one type, of which the 4a-methyl compound (1) and the steroidal 1,4-dien-3-ones are examples.They involve, for (1), either a direct alkyl shift from C-4a to C-4 and deprotonation to give a 4-alkyl-5,6,7,8-tetrahydro-2-naphthol or a shift of the 4a,5-bond from C-4a to C-8a with formation of a spiran intermediate and further ring migration from C-8a to C-1 to form a 4-alkyl-5,6,7,8-tetrahydro-1-naphthol.A further mechanism, for which there was little strong evidence, involves an alkyl shift from one angular position, C-4a, to the other, C-8a, followed by further ring migrations via a spiran intermediate to give an additional route to the 4-alkyltetrahydro-2-naphthol product.The products of rearrangement of 3,4a- and 1,4a-dimethyl-5,6,7,8-tetrahydronaphthalen-2(4aH)-ones in aqueous sulphuric acid, and in acetic anhydride with sulphuric acid catalysis, have been studied critically.The use of quantitative 13C n.m.r. spectroscopy confirms the identity and ratios of products deduced using 1H n.m.r. spectroscopy and other techniques.The results show that the third, suspect, mechanism does indeed operate, and that it contributes significantly to the formation of 4-alkyltetrahydro-2-naphthol products from both dienones.
