Diene syntheses quinones

In a synthesis of gibberellic acid, a diene and quinone, both with oxygen-substituted side chains, gave the initial intermediate. Later in the synthesis, an intramolecular D-A reaction was used to construct the A-ring. 

The student is recommended to carry out the Diels and Alder diene synthesis when making preparations from the original literature. For example, he should condense cyclo-hexadiene with quinone (Annalen. 1933, 507, 288) or furane with maleic anhydride (Ber., 1929, 62, 554). 

The diene synthesis with quinones is valuable in providing hydro-aromatic systems which are readily dehydrogenated, as illustrated by the synthesis of 2,3-dimethylanthraquinone (90% over-all). ... 

A double diene synthesis occurs with benzoquinone. With 2 molecules of cyclohexadiene, for instance, this affords the 1,4,5,8-diethanoanthracene ring system the resulting l,4,4a,5,8,8a,9a,10a-octahydro-l,4,5,8-diethanoanthra-quinone readily loses four hydrogen atoms, to give the 1,4,5,8-tetrahydro compound and, when that is heated, it spits off ethylene to afford anthraquinone ... 

Diene synthesis with quinones generated in situ O... 

Various oligoacenes have been synthesized using quinone derivatives as the dienophile in Diels-Alder reactions. One example is the synthesis of a series of epoxypolyacenequinones 19-21 by Miller et al., via repetitive Diels-Alder/oxida-tion reactions with appropriate bis-dienes and quinones. The ether-bridge could be cleaved to give the desired acene 22 with up to 11 linearly aimulated rings (Scheme 6) [25]. The final aromatization, however, has not been reported. 

Singh, V. Raju, B.N.S, p4S + p2S cycloaddition of spiro[4, ] cyclic 1,3-dienes with quinones in homogeneous and aqueous micellar media synthesis of novel polycyclic cage diones, Ind J. Chem., 1996,35B, 303-11. 

Though methods exist for the synthesis of [(NHQPd ] complexes, pal-ladium(0) species are rarely employed as pre-catalysts due to the requirement for rigorously anaerobic and anhydrous conditions. Amongst the few examples of air-stable [(NHC)Pd ] catalysts are those reported by Seller and co-workers featuring diene ° or quinone auxiliary ligands. Pd° precursors, on the other hand, are often far more robust and can be handled with greater ease, but then of course must be activated in situ to produce the catalytically active [(NHQPd ] species. 

Again a completely regioselective synthesis of 1,4-benzoxazines 157 was achieved by the [4h-2] cycloaddition of useful DIB-induced dienes o-quinone monoamines 156 with diverse vinyl ethers (Scheme 37) [53]. 

The procedure described is essentially that of Belleau and Weinberg and represents the only known way of obtaining the title compound. One other quinone acetal, 1,4,9,12-t6traoxadispiro[4.2.4.2]tetradeea-6,13-diene, has been synthesized by a conventional method (reaction of 1,4-cyclohexanedione with ethylene glycol followed by bromination and dehydrobromination ) as well as by an electrochemical method (anodic oxidation of 2,2-(l,4-phenylenedioxy)diethanol ). Quinone acetals have been used as intermediates in the synthesis of 4,4-dimethoxy-2,5-cyclohexadienone,. syw-bishomoquinone, - and compounds related to natural products. ... 

Dioxo-2, 4, 5 -trimethylcyclohexa-l, 4 -diene)-3,3-dimetbylpropi-onamide (Q). The application of this well-known acid [3-(3, 6 -dioxo-2, 4, 5 -trimethylcyclohexa-l, 4 -diene)-3,3-dimethylpropionic acid] to protection of the amino function for peptide synthesis has been examined. Reduction of the quinone with sodium dithionite causes rapid trimethyl lock -facilitated ring closure with release of the amine. 

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 actual synthesis (Scheme 10) commenced with the couphng of diene acid 54 and aminophenol 53 to provide diene amide 55. In situ generation of quinone monoimide 52 under oxidative conditions and subsequent intramolecular Diels-Alder (IMDA) reaction furnished an 8 1 mixture of endo/exo... 

Another total synthesis of elisapterosin B (27), as well as colombiasin A (36) was reported by the Rychnovsky group [39]. The underlying concept of this approach was the proposed biosynthetic pathway shown in Scheme 8. Thus, the authors decided to prepare the putative metabolite 46 in 0-methylated form 128 and subject it to Lewis acid conditions in the hope that cyclization might occur to either 27 or 36, or both. The required precursor 128 would stem from an intermolecular Diels-Alder reaction between diene 129 and quinone 130 (Scheme 20). 

Subsequent monosilylation and Wittig reaction furnished unsymmetrical double diene 170. The synthesis of the other Diels-Alder partner started from bromophenol 173 (prepared in three steps from dimethoxytoluene), which was doubly metalated and reacted with (S,S)-menthylp-toluenesulfinate 173. CAN oxidation delivered quinone 171, which underwent a Diels-Alder reaction with double diene 170 to give compound 175 possessing the correct regio- and stereochemistry. Upon heating in toluene the desired elimination occurred followed by IMDA reaction to adduct 176, which was obtained in an excellent yield and enantioselectivity. Both Diels-Alder reactions proceeded through an endo transition state the enantioselectivity of the first cyclization is due to the chiral auxiliary, which favors an endo approach of 170 to the sterically less congested face (top face) (Scheme 27). 

Lebold and Kerr reported the total synthesis of the eustifolines-A (172), -B (173), -C (93),-D (227), and glycomaurrol (92) starting from the readily available quinine imine 1574 and diene 1575 (899). This methodology uses the Diels-Alder reaction of a quinone monoimine 1574 and subsequent Plieninger indolization of the adduct 1576 for the synthesis of the key tetrahydrocarbazole framework. 

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