Cycloalkenes retro-Diels-Alder reaction

Cycloalkenes can undergo a retro-Diels-Alder reaction (Section 13.11) that produces an alkene and an alkadienyl radical cation ... 

Reviews of retro-Diels-Alder reaction have addressed the concept of transient chirality in stereoselective synthesis of functionalized cycloalkenes, and dienophiles with one or more heteroatom. The effects of pressure on retro-Diels-Alder reactions have... 

The mass spectra of cycloalkenes show quite distinct molecular ion peaks. For many cycloalkenes, migration of bonds gives virtually identical mass spectra. Consequently, it may be impossible to locate the position of the double bond in a cycloalkene, particnlarly a cyclopentene or a cycloheptene. Cyclohexenes do have a characteristic fragmentation pattern that corresponds to a retro Diels-Alder reaction (Fig. 4.4). In the mass spectrum of the monoterpene Umonene (Fig. 4.16), the intense peak at m z = 68 corresponds to the diene fragment arising from the retro Diels-Alder fragmentation. 

Diels-Alder reactions continue to be of value for the interception of highly reactive dienes or dienophiles. Thus, irradiation of 2-cyclo-octen-l-one or of 2-cyclohepten-l-one in the presence of excess cyclopentadiene affords the norbornene derivatives (173 n = 5 or 4 respectively), which undergo retro-[4 -I- 2] addition on distillation. Presumably the trans-2-cycloalken-l-ones are reactive intermediates in these processes. Elimination of acetic acid from bis(trifluoromethyl)cyclopentadienylcarbinyl acetate yields the reactive 6,6-bis(trifluoromethyl)fulvene, which rapidly dimerizes by [4 + 2] cycloaddition the fulvene intermediate can be intercepted by similar addition to cyclopentadiene. The adduct (174) is formed on reaction of cyclopentadiene with the imine produced by iodine-catalysed rearrangement of NN-... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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