2,4-Diene-1,6-diones synthesis

Novak and Sorm282 described an octa-3,5-diene-2,7-dione synthesis. Addition of diazoacetone to 2-methylfuran gave a cyclopropane derivative, which subsequently rearranged ... 

Interest in the synthesis of 19-norsteroids as orally active progestins prompted efforts to remove the C19 angular methyl substituent of readily available steroid precursors. Industrial applications include the direct conversion of androsta-l,4-diene-3,17-dione [897-06-3] (92) to estrone [53-16-7] (26) by thermolysis in mineral oil at about 500°C (136), and reductive elimination of the angular methyl group of the 17-ketal of the dione [2398-63-2] (93) with lithium biphenyl radical anion to form the 17-ketal of estrone [900-83-4] (94) (137). 

Dehydration of (105) to derivative (androsta-4,9-diene-3,17-dione [1035-69-4]) (106) provided starting material for corticosteroid synthesis... 

Madindoline A (7) and B (ent-8) are potent inhibitors of interleukin 6. In a total synthesis [21] that also intended to determine the relative and absolute configurations of these novel antibiotics, the densely functionalized cyclopen-tene-l,3-dione ring of 7 and 8 was elaborated via RCM of diene-diol 2 (Scheme 1). 

CYCLOBUTADIENE IN SYNTHESIS endo-TRICYCLO[4.4.0.02 5]DECA-3,8-DIEN-7,IO-DIONE... 

The synthesis of fUido-tricyclo[4.4.0.02 5]deca-3,8-dien-7,10-dione and verification of its endo-configuration has been reported earlier.3 This adduet is a useful starting material for the syntheses of tetracyclo-[5.3.0.02 6.03 10]deca-4,8-diene,s tricyclo[4.4.0.02 5]deca-3,7,9-triene,6 cis, syn, cjs-tricyclo[5.3.0.02,6]deca-4,8-dien-3,10-dione,7 and 4-oxahexa-cyclo[5.4.0.02 6.03 10.05 9.08,11]undecane.a... 

The recent upsurge of interest in systems of theoretical interest demands practical syntheses of several important compounds. These are BICYCLO[2.l.0]PENT-2-ENE, BENZOCYCLOPROPENE, 1,6-OXIDO[10]ANNULENE, and others. ewdo-TRICYCLO[4.4.0.02 5]-DECA-3,8-DIENE-7,10-DIONE is utilized as a model for the use of CYCLOBUTADIENE IN SYNTHESIS, and a stable monomeric ketene, icri-BUTYLCYANOKETENE offers opportunities for further studies of this interesting species. 

Novel steroidal pyridazines are readily prepared from ADC compounds and steroidal A2,4-dienes,163 A14,1 -dienes,164 and A16,20-dienes.165 ADC compounds are also commonly used in the protection of the steroid 5,7-diene system (see Section V,A). These Diels-Alder adducts of steroidal dienes and azo dienophiles should not be confused with the so-called azasteroids, which are also prepared from ADC compounds. Cyclic ADC compounds such as the pyrazole-3,5-diones (7), and the diazaquinones 12 and 13 readily add to dienes to give bicyclic pyridazine derivatives,166168 and these reactions have been adapted to the synthesis of 5,10-diazasteroids (106).42 Similarly, the 13,14-diaza- (107) and 13,14,16-triazasteroid (108) ring systems have been prepared.169... 

The product diacid has served as starting material for the synthesis of tetracycio[7.2.1.0 . 0 ]dodeca-2,7-diene-5,12-dione, C g-hexa-quinacene, (Cj)-Ci7-heptaquinane derivatives, the parent dodecahedrane mol ecu e, and a number of substituted dodecahedranes. ... 

Synthesis of the dibenzofuran (27) by irradiation of grisa-3, 5 -diene-2, 3 -dione (28) is believed to involve electrocyclic ring opening followed by intramolecular cycloaddition to the ketene and elimination of carbon dioxide, as shown in Scheme 2.24 Analogous photocyclizations are responsible for the photochromism exhibited by heterocyclic fulgides such as ( )-a-3-furyl-ethy idene(isopropylidene)succinic anhydride (29), which on irradiation... 

Similarly, HF—SbF5-induced isomerization of androsta-4,6-diene-3,17-dione 230 has been studied in detail,840 which led to a new entry into the 9-methylsterane series 231. Also, methods have been developed for the synthesis of isosterane derivatives841 and other methyl-substituted estrane dione derivatives of unnatural configurations.842 HF SbF5 superacid medium is also capable of demethylating aromatic ethers. This reaction has been successfully employed in the synthesis of 11-deoxyanthracyclines 232 [Eq. (5.305)].843... 

Sala T, Sargent MV (1981) Depsidone Synthesis. Part 16. Benzophenone - Grisa-3 ,5 -diene-2 ,3-dione - Depsidone Interconversion A New Theory of Depsidone Biosynthesis. J Chem Soc Perkin Trans 1 855... 

Diene synthesis, via palladium-catalyzed coupling, 68, 116, 130 5,6-Diethoxybenzofuran-4,7-dione, 69, 220... 

Irradiation of the 5,7-diene gave the previtamin, which was isomerized and saponified to give la-hydroxy-vitamin D3. For the last synthesis of la-hydroxy-7-dehydrocholesterol recorded here, cholesta-l,4,6-triene-3-one was again used as starting steroid.122 Deconjugation of this trienone with strong base followed by immediate reduction with calcium borohydride led to the unstable 3/3-hydroxycholesta-l,5,7-triene which, without isolation, was converted into the 1,4-addition product (265) upon reaction with 4-phenyl-l,2,4-triazoline-3,5-dione. 

This method was first applied 87) in 1972 for the synthesis of disubstituted barre-lene 83 from dione 81, which was prepared as illustrated. Photolysis of 81 in dilute solution afforded 63 % of 83 in addition to the other products shown. Neither a cyclo-butanedione nor the purported diene intermediate 82 were observed although this might be possible under appropriate conditions. 

An alternative ester synthesis, the reaction of a carboxylate anion with an alkyl halide, was used by Madejewski [62] for the preparation of ( , )-l,9-dioxacy-clohexadeca-3,1 l-dien-2,10-dione (76) under dilution conditions. This 16-membe-red dilactone represents a precursor for the synthetic norpyrenophorin 77 a, the physiological activity of which corresponds to the one of the natural products pyrenophorin 77b and vermiculin 77c. The lactone 76 can be obtained in 77% yield by dimerization of ( )-7-bromo-2-heptenic acid (75) in DMF in the presence of potassium carbonate. 

A synthesis of 22,23-epoxyergocalciferol from the 4-phenyl-1,2,4-triazoline-3,5-dione adducts (272) employed the K2CO3-DMSO reaction for deprotection of the A -diene cf. ref. 53). The Reporter observes that the assignment of the 22/3,23/3-configuration is dubious in view of earlier work in this area. " Syntheses have been reported for la,25-dihydroxy-24-nor-cholecalciferol, 25-hydroxy-24 -nor- 5,6- frans-cholecalcif erol, and 2 5 -hydroxy- 24a-homo- 5,6-... 

---