O-quinone methide imines

All attempts to trap a with dienophiles failed. However, a synthesis of the benzoquinolizidine 4 involves an intramolecular Diels-Alder reaction with an o-quinone methide imine b, generated from 3 by CsF.1... 

Intermolecular Diels-Alder Reactions of o-Quinone Methide Imines... 

Studies of the generation and properties of o-quinone methide imines38-42 (Table 9-III) suggest that with continued investigation they will prove to be useful synthetic intermediates comparable to the o-xylylenes43 and o-quinone methides.44 Although a few notable examples of successful efforts to trap the unstable o-quinone methide imines in intermolecular [4 +... 

Until recently, attempts to trap the unstable o-quinone methide imines generated by this fluoride-induced 1,4-elimination in inter-molecular Diels-Alder reactions with typical dienophiles were unsuccessful.388... 

Successful and effective examples of the in situ generation and subsequent intermolecular [4 -I- 2] cycloaddition of apparent ketene o-quinone methide imines have been detailed in the completion of total syntheses of evodiamine and rutecarpine [Eq. (18)]. ... 

Interestingly, 1-azadienes without activating groups have been shown to participate in [4 -I- 2] cycloaddition reactions. Thus, o-quinone methide imine 74, generated in situ from benzoisothiazoline 2,2-dioxides 73 by sulfur dioxide extrusion, cycloadded to methyl maleate and )V-phenylma-leimide, affording 1,2,3,4-tetrahydroquinoline-2,3-dicarboxylic acid derivatives 75 in 63-94% yield (91MI3) (Scheme 19). Earlier, Lancaster and... 

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