Decatrien-3-ones intramolecular

LP-DE also promotes and accelerates intramolecular Diels-Alder reactions of low reactive polyenones. The use of a catalytic amount of camphorsulfonic acid (CSA) further accelerates the cycloaddition and enhances the diastereo-selectivity [41]. Table 6.7 illustrates the effect of CSA on the intramolecular Diels-Alder reaction of 2-methyl-l,7,9-decatrien-3-one. 

Table 6.7 Intramolecular Diels-Alder reaction of 2-methyl-l,7,9-decatrien-3-one...

The increased stereoselectivity of decatrien-3-ones relative to the n(matrien-3-ones may also be the consequence of cooperativity between twist asynchronicity and endo stabilization that both favor the c -fused product. The decatrien-3-one transitirm state is considerably less strained than the nonatrien-3-one transition state, and the uncatalyzed decatrienone cyclizations occur at or near ambient temperature. Consequently, one expects greater endo stabilization, and hence also greater cis stereoselectivity, in the decatrienone intramolecular Diels-Alder reactions. 

A conceptually different synthetic approach to substituted derivatives of (7f)-l, 7,9-dccatrien-3-one has been described23 Reaction of silyloxycyclopropanc-containing trienes with hydrogen fluoride gave (, )-l,7,9-decatrien-3-one derivatives, which underwent intramolecular [4 + 2] cycloaddition under various conditions. 

Microwave-assisted tandem Witting intramolecular Diels-Alder cycloaddition of ester tethered 1,3,9-decatrienes to give 3,4,4a,7,8,8a-hexahydroisochromen-1-ones was reported with high yields (53-89%) (Wu et al., 2011). Three consecutive carbon-carbon bonds in the end product were formed rapidly during this tandem process under the microwave irradiation efficiently. 

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