Parham-type cyclization

Moreau A, Courure A, Deniau E, Grandclaudon P (2005) Construction of the six- and five-membered aza-heterocyclic units of the isoindoloisoquinolone nucleus by parham-type cyclization sequences - total synthesis of Nuevamine. Eur J Org Chem 3437-3442... 

Fused pyrazole compounds have been prepared from A -alkyl-substituted pyrazoles. For example, a palladium-catalyzed/norbornene-mediated sequential coupling reaction involving an aromatic sp C-H functionalization as the key step has been described, in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one pot. A variety of highly substituted six-membered annulated pyrazoles 433 were synthesized in a one-step process in moderate yields from iV-bromoalkyl pyrazoles 431 and aryl iodides 432 (Equation 87) <20060L2043>. An intramolecular cyclization version has also been reported. Exposure of 2equiv of -butyllithium to l//-pyrazole-l-alkanoic acids 434 afforded the cyclic ketones 435 via a Parham-type cyclization process (Equation 88) <1997SL1013>. 

The utility of o-quinodimethanes as very reactive diene components in Diels-Alder reactions has stimulated interest in the synthesis of benzocyclobutanes, their most commonly used precursors. A full account has been given of the preparation of benzocyclobutanols (47) from o-halostyrene oxides (46), " whereas a related Parham-type cyclization can be used to convert bromoethyl-benzenes (48) into benzocyclobutanes (49). Two rather different approaches... 

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