Diels asymmetric, decalins

Application of this catalytic process was extended to asymmetric intramolecular Diels-Alder reactions. Synthetically useful intermediates with octalin and decalin skeletons were obtained in high optical purity by use of a catalytic amount of the chiral titanium reagent [45] (Scheme 1.57, Table 1.25). The core part of the mevi-nic acids was enantioselectively synthesized by use of this asymmetric intramolecular reaction [46] (Scheme 1.58). 

A Lewis acid-mediated two-fold asymmetric Michael addition allows access to c( s-decalin derivatives. The reaction of the trimethylsilylenol ether of acety Icyclohexene with phenylmenthyl acrylate in the presence of Diethylaluminum Chloride (eq 7) yields the decalone in 64% yield (70% de). This has been shown not to be a Diels-Alder reaction. If the reaction is worked-up early, the initial Michael adduct can be isolated. ... 

Asymmetric Diels-Alder reactions of the chiral dienophile 5-(alkyloxy)-5 /-2-furanone (D), derived fi om the chiral auxiliary 10, with a variety of dienes have been studied in toluene at 120°C. Thereby, diastereoselectivities up to 96% de were determined. From cyclic dienes with exocyclic or vinylic double bonds, such as (3), substituted decalins were obtained as optically pure cycloadducts. 

In 2013, Liao reported the first asymmetric total syntheses of the sesquiterpenoid lactones (+)-eudesmadiene-12,6-olide and (+)-fruUanolide, which were based oti an initial dearomatization of 4-bromo-2-methoxyphenol 240 into the corresprMidmg MOB 241 (Fig. 58) [129]. An asymmetric Diels-Alder reaction wifli the chiral furan R)-2A2 furnished the bicyclo[2.2.2]octenone 243 in good yield with high chemo-, regio-, and stereoselectivities. This compound was further transformed in a few steps to reach (+)-eudesmadiene-12,6-olide, whose m-decalin core was elaborated by a high-yielding anionic oxy-Cope rearrangement of the allylic alcohol 244 (Fig. 58) [129]. 

In recent screening for the best catalyst for an asymmetric Diels-Alder reaction between fumarate and cyclopentadiene, BiCls gave poor stereoselectivity (Equation 23) [40b]. The same result was obtained when BiCla was tested in catalysis of asymmetric ionic Diels-Alder for the synthesis of cis-decalins [41]. 

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