Cyclohex-l-en-3-one

Robinson Annulation Sequential Michael addition/aldol condensation between a ketone enolate and an alkyl vinyl ketone (i.e. MVK) to give a cyclohex-2-en-l-one... 

Methyl-l,2,3,9-tetrahydro-4H-carbazol-4-one, the key building block of the neuroactive compound alosetron, was easily obtained from 3-[(2-halophenyl)(methyl)amino]cyclohex-2-en-l-one by pyrrole ring formation via Heck reaction under microwave irradiation [94], While the iodo substrate gave an excellent yield in only 30 min at 100 °C the corresponding bromo derivative converted only poorly under the same reaction conditions (Scheme 88). 

The Birch reduction has been used by several generations of synthetic organic chemists for the conversion of readily available aromatic compounds to alicyclic synthetic intermediates. Birch reductions are carried out with an alkali metal in liquid NH3 solution usually with a co-solvent such as THF and always with an alcohol or related acid to protonate intermediate radical anions or related species. One of the most important applications of the Birch reduction is the conversion of aryl alkyl ethers to l-alkoxycyclohexa-l,4-dienes. These extremely valuable dienol ethers provide cyclohex-3-en-l-ones by mild acid hydrolysis or cyclohex-2-en-l-ones when stronger acids are used (Scheme 1). 

A structural requirement for the asymmetric Birch reduction-alkylation is that a substituent must be present at C(2) of the benzoyl moiety to desymmetrize the developing cyclohexa-1,4-diene ring (Scheme 4). However, for certain synthetic applications, it would be desirable to utilize benzoic acid itself. The chemistry of chiral benzamide 12 (X = SiMes) was investigated to provide access to non-racemic 4,4-disubstituted cyclohex-2-en-l-ones 33 (Scheme 8). 9 Alkylation of the enolate obtained from the Birch reduction of 12 (X = SiMes) gave cyclohexa-1,4-dienes 32a-d with diastereoselectivities greater than 100 1 These dienes were efficiently converted in three steps to the chiral cyclohexenones 33a-d. 

In 1989, Isobe and coworkers reported on an organometallic polyoxometalate cluster [(Rhcp )4V60i9] (cp = /j -CsMcs) that catalyzes the oxidation of cyclohexene with TBHP as oxidant to give mainly ally lie oxidation products (l-ferf-butylperoxycyclohex-2-ene 42% and cyclohex-2-en-l-one 21%) and only little epoxide (15%) (equation 62). The yield of 1 -ferf-butylperoxy cyclohex-2-ene increased with decreasing molar ratio of cyclohexene to TBHP, while the yield of cyclohex-2-en-l-one has a maximum at the ratio of 0.2. 

Crotonic acid, cis Sd (roasted) ° Crotonic acid, trans Sd (roasted) ° Cryptochlorogenic acid Sd 0.4-2.63% Cyanidin-3 diglucoside Fr Cyclohex-2-en-l-one, 3-methyl Sd CycIohexan-l-2-dione, 3-methyI Sd (roasted) ... 

A regioselective and highly syn-stereoselective catalyst-free intermolecular alkylation of aryl borates with aryl epoxides under mild, neutral conditions has been reported.27 The reaction of /ra .s-stilbene oxide with tri(3,5-dimethylphenyl)borate gave a 38% yield (>95% syn) of the C-alkylated product (13), easily separated from (g) the O-alkylated product(s). Triflic anhydride has been used to activate enones to nucleophilic attack by electron-rich arenes in the presence of a sterically hindered base.28 Resorcinol dimethyl ether, for example, reacted with cyclohex-2-en-l-one to... 

Reagents i, LiBH4, THF ii, SOCl2 iii, NaOMe iv, Mg, THF, then 3-ethoxy-cyclohex-2-en-l-one ... 

No substitution product is formed with the enolate ion of cyclohex-2-en-l-one. However, this anion is quite reactive at the initiation step and is often used as an entrainment reagent [17]. Under photo stimulation, the best yields of heteroarylation and phenylation of the enolate ions from aromatic ketones are obtained in DMSO [18]. 

Acid-catalyzed halogenation is synthetically useful for converting ketones to a,/3-unsaturated ketones, which are useful in Michael reactions (Section 22-18). Propose a method for converting cyclohexanone to cyclohex-2-en-l-one, an important synthetic starting material. 

Ans. Methyl cyclohex-2-en l-one and methyl cyclohex-2-en l-ol. Allylic stabilization of R. ... 

Triazines usually react with dienophiles to afford pyrimidines (Scheme 58), or similarly with cyclohex-2-en-l-ones producing 5,6,7,8-tetrahydroquinazoline-ketones <2002TL3551>. 

Other Degraded Carotenoids. The acetylenic diol (115), prepared by reaction of but-3-yn-2-ol dianion with 2,6,6-trimethyl-4,4-ethylenedioxycyclohex-2-en-l-one (116), afforded 3,5,5-trimethyl-4-(2-butenylidene)-cyclohex-2-en-l-one (117), a major constituent of Burley tobacco, on LiAlH4 reduction and hydrolysis.53... 

Cyclohepta[4,5)pyrrolo[l,2-fl]imidazoles, 2-aryl-, halogenation. 59, 283 Cyclohepta[4,5)pyrrolo[3,2-e][l,2,4]triazine, 3-chloro- 10-(4-chlorobutyD-5,6,7,8,9,10-hexahydro-, 59, 50 3//-Cyclohept(e]isoxazoles, 3a,4,5,6,7,8-hexahydro-, 60, 311-3 Cyclohex-2-en-l-ones, 2- and 3-bromo-, regioselectivity of nitrile oxide cycloaddition, 60, 304 Cyclols, piperazine-2,5-dione-related, 57, 211-7... 

Although chiral induction has been observed in the Michael addition of various benzenethiols to l,4-systems such as cyclohex-2-en-l-one (15). in the presence of chiral, N-substituted porphyrin bases only the racemic mixture is obtained for pentafluorobenzenethiol (6), albeit in high chemical yield. ... 

The reaction appears to be general, although a limited number of examples have been reported. A particularly useful process begins with meta addition to anisole-Cr(CO)3, followed by protonation and hydrolysis of the enol ether unit. The result is a 5-substituted cyclohex-2-en-l-one. This dienol ether can be isolated in high yield before the aqueous hydrolysis. 

The complex [OsHBr(CO)(PPh3)3] is effective for the selective hydrogenation of conjugated and non-conjugated dienes to monoenes, and this complex also catalyzes the hydrogenation of linear and cyclic alkenes. (-)-Carvone (9) is selectively reduced to 2-methyl-5-(l-methylethyl)cyclohex-2-en-l-one (10) or 2-methyl-5-(l-methylethyl)cyclohexanone (11), depending on the reaction conditions. ... 

A report on the preparation of various substituted naphthylcyclohexane derivatives describes the use of 3-(6-methoxy-2-naphthyl)cyclohex-2-en-l-one (320) as a key intermediate. Condensation between 2-(j5-dimethylamino-propionyl)-6-methoxynaphthalene (319b), readily obtained from 6-methoxy-2-acetylnaphthalene (319a), and acetoacetic ester afforded (320), after hydrolysis... 

Free-radical processes are also present in the cyclohexene oxidation, giving cyclohex-2-en-l-ol and cyclohex-2-en-l-one (22). 

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