Thioesters Diels-Alder reactions

Fluorinated heterodienophiles and heterodienes Diels-Alder reactions in which the dienophiles have perfluoroalkyl-substituted multiple bonds between carbon and a heteroatom are quite common Reported earlier were reactions of perfluoroketones, thiones, ketimines, thioesters, nitroso compounds, and nitriles [9] Examples of a-fluoroimines [107], co-hydroperfluorothioaldehydes [108], perfluorosulfines [109, IIO], and selenocarbonyidifluoride [III] (equations 89-92) have been reported recently... 

The success of bis(oxazoline)-copper(II) catalyzed Diels-Alder reactions involving acryloylimides as dienophiles has been extended to the Michael reaction, Eqs. 204 and 205. The observed enantiofacial discrimination in the Diels-Alder reactions was expected to translate well to Michael reactions involving enolsilanes as nucleophiles. Indeed, fumarate-derived imides afford Michael adducts of enolsilanes in high enantioselectivity (240). Diastereoselectivity in these reactions may be regulated by judicious choice of thioester and enolsilane geometry to provide either diastereomer in high selectivity (>99 1 syn or 95 5 anti). 

Dienes coordinated to iron tricarbonyl do not undergo Diels-Alder reactions and a number of interesting annulation reactions of groups attached to iron tricarbonyl diene complexes have been developed. Cyclohexadiene iron tricarbonyl complexes having a pendant alkene undergo annulation reactions to form spirocychc compounds (Scheme 160). Related reactions of allylic thioesters afford spirocychc thialac-tones. 

Because of their previous findings that a, -unsaturated thioesters were more reactive than their ester counterparts in Diels-Alder reactions , Hart and coworkers performed a systematic study of the cycloaddition reactions of a, -unsaturated thioesters and a,fi-unsaturated selenoesters with several dienes. Thermal reactions were compared with Lewis acid catalyzed reactions at room temperature (equation 28 and Table 2). The results clearly demonstrated that use of a Lewis acid enhanced the regioselectivity (entries 1 vi 2, 3 vs 4, 5 vs 6 and 7 vs 8) as well as the endo (with respect to the thioester or selenoester group) selectivity (entries 5 vs 6 and 7 vs 8). 

Mercuracarborand 17 and octamethyl derivative of 10. (9.12-Me2-o-C2BioH8Hg)4 (20) were applied as catalysts for the Diels-Alder reaction of a thionoester trans-MeCH=CHC(S)OMe with cyclopentadiene. It was found that on carrying out the reaction in CH2CI2 at in the presence of 20 (diene 20=7.5 E [thioester]o= 1 M)... 

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