Quinone methides synthesis

Amouri, H. Vaissermann, J. Rager, M. N. Grotjahn, D. B. Rhodium-stabilized o-quinone methides synthesis, structure, and comparative study with their iridium congeners. Organometallics 2000, 19, 5143-5148. 

Lemus, R. L. Lee, C. H. Skibo, E. B. Studies of extended quinone methides. Synthesis and physical studies of purine-like monofunctional and bifunctional imidazo[4,5-g]quinazo-line reductive alkylating agents. J. Org. Chem. 1989, 54, 3611-3618. 

This addition is general, extending to nitrogen, oxygen, carbon, and sulfur nucleophiles. This reactivity of the quinone methide (23) is appHed in the synthesis of a variety of stabili2ers for plastics. The presence of two tert-huty groups ortho to the hydroxyl group, is the stmctural feature responsible for the antioxidant activity that these molecules exhibit (see Antioxidants). 

Quinone methides have been shown to be important intermediates in chemical synthesis,1 2 in lignin biosynthesis,3 and in the activity of antitumor and antibiotic agents.4 They react with many biologically relevant nucleophiles including alcohols,1 thiols,5-7 nucleic acids,8-10 proteins,6 11 and phosphodiesters.12 The reaction of nucleophiles with ortho- and /iara-quinone methides is pH dependent and can occur via either acid-catalyzed or uncatalyzed pathways.13-17 The electron transfer chemistry that is typical of the related quinones does not appear to play a role in the nucleophilic reactivity of QMs.18... 

Van De Water, R. W. Pettus, T. R. R. cx-Quinone methides intermediates underdeveloped and underutilized in organic synthesis. Tetrahedron 2002, 58, 5367-5405. 

Amouri, H. Besace, Y. Bras, J. L. Vaissermann, J. General synthesis, first crystal structure, and reactivity of stable o-quinone methide complexes of Cp Ir. J. Am. Chem. Soc. 1998, 120, 6171-6172. 

The UV-Vis spectral detection of an intermediate in the catalytic reductive alkylation reaction provides only circumstantial evidence of the quinone methide species. If the bioreductive alkylating agent has a 13C label at the methide center, then a 13C-NMR could provide chemical shift evidence of the methide intermediate. Although this concept is simple, the synthesis of such 13C-labeled materials may not be trivial. We carried out the synthesis of the 13C-labeled prekinamycin shown in Scheme 7.5 and prepared its quinone methide by catalytic reduction in an N2 glove box. An enriched 13C-NMR spectrum of this reaction mixture was obtained within 100 min of the catalytic reduction (the time of the peak intermediate concentration in Fig. 7.2). This spectrum clearly shows the chemical shift associated with the quinone methide along with those of decomposition products (Fig. 7.3). 

SCHEME 7.21 Synthesis of a stable quinone methide using rhodium (II) acetate in methanol.84,93 The 13C label is designated with an asterisk ( ). 

NATURAL DITERPENE AND TRITERPENE QUINONE METHIDES STRUCTURES, SYNTHESIS, AND BIOLOGICAL POTENTIALS... 

Mori, K. Matsui, M. Diterpenoid total synthesis. XIII. Taxodione, a quinone methide tumor inhibitor. Tetrahedron 1970, 26, 3467-3473. 

Sanchez, A. J. Konopelski, J. P. Phenol benzylic epoxide to quinone methide electron reorganization synthesis of ( )-taxodone. J. Org. Chem. 1994, 59, 5445-5452. 

Angle, S. R. Rainer, J. D. Woytowicz, C. Synthesis and chemistry of quinone methide models for the anthracycline antitumor antibiotic. J. Org. Chem. 1997, 62, 5884-5892. 

Colloredo-Melz, S. Dorr, R. T. Verga, D. Freccero, M. Photogenerated quinone methides as useful intermediates in the synthesis of chiral BINOL ligands. J. Org. Chem. 2006, 71, 3889-3895. 

Landucci, L. L. Ralph, J. Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 1. Synthesis and characterization. J. Org. Chem. 1982, 47, 3486-3495. 

Zanarotti, A. Synthesis and reactivity of vinyl quinone methides. J. Org. Chem. 1985, 50, 941-945. 

Zanarotti, A. Preparation and reactivity of 2,6-dimethoxy-4-allylidene-2,5-cyclohexa-dien-l-one (vinyl quinone methide). A novel synthesis of sinapyl alcohol. Tetrahedron Lett, 1982, 23, 3815-3818. 

The pyrano[3,2-c][l]benzopyran system is available from the reaction between salicylaldehyde and 5-phenylthio-4-penten-l-ols which proceeds by an intramolecular cycloaddition of an o-quinone methide desulfurisation is facile (Scheme 29) <00TL2643>. Mild conditions have been established for the synthesis of (-)-hexahydrocannabinol 50 from the olivetol derivative 49 which also involves a quinone methide (Scheme 30) <00SC1431>. 

The groups of Liebeskind and Moore independently explored the ring expansion of allenyl-substituted cyclobutenol derivatives. This allows either the preparation of 5-alkylidene-2-cyclopentenones, which are substructures of naturally occurring bioactive compounds [59], or the generation of o-quinone methides, which are very attractive intermediates in the synthesis of hexahydrocannabinols [109]. As shown in Scheme 8.42, the ring expansion of the tetrasubstituted methoxyallene derivative 170 furnished the vinylhydroquinone 172 in high yield [109]. 

In the synthesis of an euglobal skeleton, a quinone methide has been generated Y Y in situ by anodic oxidation mediated... 

Cycloaddition Anodically generated phe-noxy cations, o-quinones, and o-quinone methides react with olefins to bicyclic and tricyclic annelated compounds in stereoselective cycloadditions [250-252]. In the synthesis of a Euglobal skeleton, a quinone methide has been generated in situ by anodic oxidation mediated by DDQ. The cycloaddition was promoted by the use of lithium perchlorate... 

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