Alkyl-substitution effects in the photochemistry of 2-cyclohexenenones

NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer

“…The dialkylcylohexenones were prepared from the abovementioned dialkylacetaldehydes 2 (0.1 mol scale) and methyl vinyl ketone (3), following the general procedure of Dauben and coworkers for the synthesis of 6a (Dauben et al, 1968). In the case of enones 6a-d, the crude product was chromatographed on silica gel, eluting with petroleum ether/ethyl acetate (90:10), giving the desired product in a 70-85% yield.…”

Reaction of β-halo α, β-unsaturated ketones with cuprate reagents. Efficient syntheses of β, β-dialkyl ketones and β-alkyl α,β-unsaturated ketones. A synthesis of (Z)-jasmone

“…In fact, the major product of this reaction was the crystalline 2-methyl-3-phenylthio-2-cyclopenten-1-one (49), showing that, in this case, phenylthio transfer was more facile than methyl t r a n~f e r .~ It was subsequently found, however, that the formation of 49 could be avoided nearly completely by use of the iodo enone 50 in place of the corresponding bromo compound 19. Thus, treatment of 50 with the cuprate reagent 44 afforded 2,3-dimethyl-2-cyclopenten-1-one (40) in high yield.…”

“…Although lithium (phenylthio)(methyl)cuprate (44) efficiently transformed the 3-bromo-2-cyclohexen-1-ones 12, 14, and 15-17 into the corresponding P-methyl enones (Entries 1-5), a similar reaction of 44 with the P-bromo cyclopentenone 19 afforded 2,3-dimethyl-2-cyclopenten-1-one (40) in very poor yield (Entry 6). In fact, the major product of this reaction was the crystalline 2-methyl-3-phenylthio-2-cyclopenten-1-one (49), showing that, in this case, phenylthio transfer was more facile than methyl t r a n~f e r .~ It was subsequently found, however, that the formation of 49 could be avoided nearly completely by use of the iodo enone 50 in place of the corresponding bromo compound 19.…”

Photocycloaddition Reactions of 5,5‐Dimethyl‐3‐(3‐methylbut‐3‐en‐1‐ynyl)cyclohex‐2‐en‐1‐one

“…-Cyclohex-2-enones 1 undergo photodimerization to mixtures of (regioisomeric) tricyclo[6.4.0.0 2,7 ]dodecanediones 2 and 3, the relative ratio of these tricyclic dimers depending on the polarity of the solvent [1 -3]. This is exemplified in Scheme 1 for 5,5-dimethylcyclohex-2-enone (1a) [4] or isophorone (¼ 3,5,5-trimethylcyclohex-2-enone; 1b) [5] [6]. Both of these photoexcited enones also react efficiently with alkenes [7] to afford bicyclo[4.2.0]octan-2-ones 4.…”