Cyclopentene carbaldehydes

Dialdehydes have been converted to cyclopentene carbaldehydes via an intra- molecular asymmetric aldol cyclodehydration, using hydroxyamino acids as catalysts.130... 

The synthesis of prostaglandin PGB1 as described by Morin et al. (Eli Lily Research Labs.), starts with 7-(2-methoxyphenyl)heptanoic acid 142 which is converted into 143 through Birch reduction, esterification and acetalization. Ozone cleavage of 143 and cyclization of the resulting dialdehyde affords cyclopentene carbaldehyde 144 which was subjected to ( )-selective Wittig olefination with... 

The cyclopentene-carbaldehyde 39 reacts with the enol-ether 40 to form the adduct 41, having the skeleton of 3-oxobicyclo[4.3.0]non-l-ene. An alcohol has been then regioselectively and stereoselectively added ( compound 42 ) at the double bond from... 

Complexes of nickel(II) or magnesium(II) with the chiral ligand DBFOX (Scheme 8) catalyze the DCR of nitrones with a-alkyl- and arylacroleins rendering preferentially the 5-carbaldehyde cycloadducts. However, the reactions with a-bromoacrolein catalyzed by the zinc(II) complex of the same ligand afford isoxazoline -carbaldehydes. The corresponding cobalt(II) complex is also active for the cycloaddition between cyclopenten-l-carbaldehyde and diphenylnitrone. 

The conversion of this dialdehyde to cyclopentene-l-carbaldehyde is an intramolecular aldol condensation and is achieved by treatment with potassium hydroxide. 

As the reaction was actually carried out, cyclopentene-l-carbaldehyde was obtained in 58% yield from Iratis-1,2-cyclohcxancdiol by this method. 

P,y-Unsaturated aldehydes are a family of carbonyl compounds that have been considered ODPM unreactive for many years. This conclusion was based on literature precedents that indicated that the normal photochemical reactivity of such compounds, both on direct and sensitized irradiation, was decarbonylation to the corresponding alkene. > f> Thus, compounds 5, 6, 7, and 8 are representative examples of a series of steroidal and cyclic P,y-unsaturated aldehydes, studied by Schaffner et al. about 20 years ago, that undergo decarbonylation on irradiation. Diirr et al. have studied the photochemistry of some aryl-substituted-2-cyclopentene-l-carbaldehydes 9. In this instance, ds-stilbene-type electrocy-clic cyclization and decarbonylation were the only reactions observed. Other authors have also reported the decarbonylation of the acyclic P,y-unsaturated aldehydes 10 and 11 on direct irradiation. 

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