Inter-intermolecular three-component reaction

Scheme 8.34 An inter-intermolecular three-component reaction [338aj.

Synthesis of furans has been carried out via three-component reactions involving intermolecular carbonyl ylide formation. Johnson and co-workers have revealed [65] the consequence of intermolecular carbonyl ylide generation followed by trapping with a selective dipolarophile to obtain furan ring systems. On the basis of this approach, the diazosulfone 8 underwent intermolecular reaction with aldehydes in the presence of Rh2 (oct)4 to form carbonyl ylide intermediates, which could be trapped by alkynes in an inter-or intramolecular manner to yield substituted dihydrofurans 9 or 11, which were later converted to furans 10 and 12, respectively (Scheme 2). 

An efficient and also elegant synthesis of the active anti-influenza A virus indole alkaloid hirsu-tine 67 is performed by an inter-intermolecular anionic-pericyclic three- component domino reaction followed by solvolysis and hydrogenation (scheme 13).[261 The synthetic sequence developed by us contains first a Knoevenagel condensation of enantiopure 61 and 62 with the formation of the... 

Early on, Heck and co-workers found that intra- and intermolecular coupling reactions of haloalkenes with alkenes in the presence of secondary amines gave allylamines.t t Apparently, an intermediate 7r-allylpalladium complex is formed by rearranganent of the (7-homoallylpalladium intermediate (see above, B.ii) and in turn attacked by the nitrogen nucleophile. Excellent yields of tertiary aUylamines are obtained in this three-component coupling (Scheme As far as the outcome is concerned, analogous inter-intra- as well as fully intramolecular processes have been estabhshed (Scheme 30 see Table... 

This chapter contains a survey of free-radical-mediated multicomponent reactions (MCRs), which permit the coupling of three or more components. Even though they are not technically classified as MCRs, remarkable intramolecular radical cascade processes have been developed. Some examples, such as those shown in Scheme 6.3, use an isonitrile or acrylonitrile as the intermolecular component for each reaction [6]. These examples demonstrate the tremendous power of the combination of inter- and intramolecular radical cascade processes in organic synthesis. Readers are advised to be aware of remarkable intramolecular aspects of modem radical chemistry through excellent review articles published elsewhere [1, 7]. It should also be noted that there has also been remarkable progress in the area of living radical polymerizations, but this will not be covered here. 

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