Cyclohexa-2,5-diene-1 -one

A solution of 4-(tributylsiloxy)-4-(trifluoromcthyi)cyclohexa-2,5-dien-1-one (3.9 g. 10 mmol) in abs EtOH (10 mL) was treated successively with Zn dust (1.3 g. 20 mmol) and HOAc/H.O (4 1,10 mL). The mixture was heated to reflux for 1 h, allowed to cool to rt. and poured into HjO (100 mL). The resulting aqueous mixture was extracted with EtjO (3x.50mL). Combination, drying (MgSO ) and concentration of the FtjO layers afforded a residue, which was purified by short-path distillation to give the phenolic product yield 0.8 g (47%) bp 60 65 C/5 Torr. 

Waring, A. J., Zaidi, J. H., Pilkington, J. W. Dienone-phenol rearrangements of bicyclic cyclohexa-2,5-dien-1-ones kinetic studies of the importance of a multistage mechanism. J. Chem. Soc., Perkin Trans. 21981, 935-939. 

Substituted alkylperoxy- 165 (R = alkyl) and hydroperoxy-cyclohexa-2, 5-diene-1-ones 165 (R = H) having properties of thermo- and photoinitiators and formed from phenolic AO in sites with high concentration of ROO or with excited sensitizers do not reduce the effect of 28 even when used in concentrations exceeding those in the real system [263,264], An enhanced formation of NO from 28 (R = H) in heptane in the presence of 165 R = H, ferf-butyl) in comparison with heptane doped with 2,6-di-ierf-butyl-4-methylphenol reveals that 28 deactivates the peroxidic species 165. A similar mechanism as that taking place with alkylhydroperoxides was expected. 

Intramolecular conjugate addition reactions of 4,4-disubstituted cyclohexa-2,5-dien-1-ones have been described within the context of an approach to manzamine A (Scheme 26). ° ... 

Bis-allylic oxidation of 23 and related cyclohexa-1,4-dienes provides a convenient and general preparation of cyclohexa-2,5-dien-l-ones (Scheme 7). These cross-conjugated die-nones are substrates for a variety of photochemical rearrangement and intramolecular cycloaddition reactions. Amide-directed hydrogenations of dienones 24a and 24b with the homogeneous iridium catalyst afford cyclohexanones 25a and 25b, containing three stereogenic centers on the six-... 

The 1,2-shift of pcrfluoroalkyl groups from carbon to carbon has been reported in an acyloin-like rearrangement of 4-hydroxy-4-(perfluorooctyl)cyclohexa-2,5-dien-l-one (19) to hy-droquinone 20.13... 

Photoirradiation of inclusion crystals of the 4-(3-butenyl)cyclohexa-2,5-dien-l-ones (83) with the optically active host compounds (12c) in the solid state gave optically active l-carbomethoxytricyclo[4.3.1.0]dec-2-en-4-ones (84). For... 

Reaction with p-benzoquinones.6 Fischer and Henderson have found conditions that result in 1,2-addition of various RLi reagents to p-bcnzoquinonc. The reaction when conducted in ether at —78° results in 4-alkyl-4-hydroxycyclohexa-2,5-diene-l-ones. These products undergo further 1,2-addition with RLi in THF to give dialkyl-cyclohexa-2,5-diene-1,4-diols. Mixed dienediols can be obtained by use of two different RLi reagents. 

Parallel to this reaction, an isomerization process of 2,3,4,4,6-pentachloro-cyclohexa-2,5-dien-l-one 2 in pentachlorophenol 1 takes place. 

Intramolecular hydroamination of cyclohexa-2,5-dienes has afforded the corresponding bicyclic allylic amines with high selectivity (Scheme 13).80 The reaction does not proceed through a direct hydroamination of one of the diastereotopic alkenes but more likely involves a diastereoselective protonation of a pentadienyl anion, followed by addition of a lithium amide across the double bond of the resulting 1,3-diene and a highly regioselective protonation of the final allylic anion. 

An aq. soln. of 2-bromo-N-ethyl-4 -hydroxybenzanilide, NaOH, and NaBH4 irradiated 1.25 hrs. with a 100 w. high-pressure Hg-lamp 2 -ethyl-4-hydroxy-spiro(cyclohexa-2,5-diene-l,l -isoindolin)-3 -one. Y 62% based on startg. m. consumed. Z. Horii et al., Chem. Commun. 1970, 1039. 

Cyclobutane formation via light-induced [2 + 2] cycloaddition is probably one of the best studied photochemical reactions and has been reviewed thoroughly up to 1972 (Houben-Weyl, Vols. 4/5 a and 4/5 b). The most important types of C —C double-bond chromophores undergoing such reactions arc alkenes, 1,3-dienes, styrenes, stilbenes, arenes, hetarenes, cycloalk-2-enones, cyclohexa-2,4(and 2,5)-dienones, 1,4-benzoquinones, and heteroanalogs of these cyclic unsaturated carbonyl compounds. For p notocyciodimerizations see Houben-Weyl, Vol. 4/5 a, p 278 and for mixed [2 + 2] photocycloadditions of these same chromophores to alkenes see Section 1.3.2.3. 

Cyclohexadienones of the type IV (n = 0, 1, 2)29 are formed from 2,2 -bi-phenyldiols, 2,2 -methylenebisphenols or 2,2 -ethylenebisphenols via intramolecular C-0 coupling. 5, 7, 3 , 5 -Tetra-tert-butylspiro [2,3-dihydrobenzofuran-2,P-cyclohexa-3 , 5 -diene-2 -one] (IV, R1 = R2 = tert-Bu, n = 1) is stable. The similar compound IV (R1 = tert-Bu, R2 = Me, n = 1), prepared from the technically important antioxidant 2,2 -methylenebis (4-methyl-6-tert-butylphenol) by oxidation with sodium hypochlorite30 is oily and crystallizes in the form of Diels-Alder addition compound V. 

Part structure A is recognised to be a 2,5-disubstituted cyclohexa-1,3-diene on the basis of its chemical shift values. The ethyl group is one substituent, the other is a carboxy function judging by the chemical shift value of 8c = 174.1. The CH multiplicities which follow from the DEPT subspectra, 2C, 4CH, 5CH2 and CHj, lead to the CH part formula C2 + C4H4 + CsHw + CH3 = C12///7. Comparison with the given molecular formula, Ci2/7j 03, indicates an OH group. Since... 

---