Cydohex-2-enone

Meyer, L., Alouane, N., Schmidt, K., and Margarefha, P. (2003) Photocydoaddition of cydohex-2-enones to acrylonitrile. Canadian Journal ofChemistry, 81,417—422. 

The simplest example of this type of transformation, a type of reversed Birch reduction, is the conversion of cydohex-2-enone to phenyl ethyl ether in 93% yield by treatment with 2 equivalents of the ethoxy dichlorovanadium compound, VCHOEQCIj under an oxygen atmosphere which resulted in a faster reaction rather than with nitrogen or in a toluene solution (ref.72). 

Dodeca-4,6,8-triynedioic acid 17b (21.8 mg) was dissolved in 8 mL EtOAc. After dodeca-4,6,8-triynedioic acid was completely dissolved 3-[(pyridin-4-ylmethyl)-amino]-cydohex-2-enone (20a) was added followed by 1.0 mL of methanol. The reaction was heated and stirred until the reactants dissolved. The mixture was then allowed to slowly evaporate at room temperature during which time red crystals precipitated, mp 144—145 °C. X-ray crystallography demonstrated these to be the host-guest complex 20a-17b. Irradiation of this complex with a Co y-ray source (0.8 Mrad h ) for 80 h resulted in a slow conversion to the poly(triacetylene). 

Tridachiahydropyrone belongs to the family of marine polypropionates [69]. Efforts towards its total synthesis have recently led to a revision of the structure with the new proposal 2-147 [70]. The construction of the highly substituted cyclohex-enone moiety 2-146 which could be incorporated into this natural product [71] has been described by Perkins and coworkers (Scheme 2.33) [70, 72]. The conjugate addition/ Dieckmann-type cydization utilizing organocopper species as Michael donors afforded the enantiopure 2-145 in 68% yield. A further methylation of the (3-ketoester moiety in 2-145 followed by an elimination led to the desired cydohex-enone 2-146. 

Chiral phosphoric adds also catalyze [4+2] cydoadditions. Gong and colleagues showed that 99c activates aromatic aldehydes 207, anisidine (119), and cydohex-enone (206) to give the hctero-Diels-Alder products 208 and 209 with good yield and enantioselectivity, along with moderate endo-selectivity (Scheme 42.48) [104]. 

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