Anthracene derivative, preparation

Cyclotriveratrylene was first prepared by Gertrude Robinson in 1915 (Scheme 7.2). Robinson was interested in following up earlier work on the synthesis of anthracene derivatives and concluded that her product (empirical formula, C7H10O2, was 2,3,6,7-tetramethoxy-9,10-dihydroanthracene (7.43), the dimer of the intermediate veratryl cation (7.42). During the 1950s, CTV was again reformulated erroneously as a hexamer (7.44) and it was not until 1963 that the onset of a variety of modern techniques established a trimeric formula. 

A number of anthracene derivatives have been prepared that take advantage of this approach. Two excellent examples are 9-nitroanthracene (9) [23] and anthryl trifluoromethyl ketone (10) [24], Both of these molecules, with strongly electron-withdrawing groups, adopt a nearly columnar it-stacked arrangement in the crystal (Fig. 14.7). The separations between the it-faces of these stacked molecules (the parameter with the most dramatic impact on charge transport [7]) are 3.53 A (9) and 3.56 A (10). 

A well established procedure for the synthesis of methylenemalonate 2-111 is the thermolysis of the anthracene derivative 2-110 [134a]. Recently, also a new method for the preparation of the useful methylidene-Meldrum s acid has been described [134b]. 

Transannular peroxides of anthracene and its derivatives, preparation, properties, applications of 90CLY582. 

The first thiete fused to an aromatic system 219 (and an anthracene derivative) was reported in 1965 and was prepared by reduction of a naphthothiete sulfone. An attempt to prepare benzothiete by desulfurization of benzo-l,2-dithiolane was unsuccessful. Photolysis of benzo-l,2-dithiolane 1,1-dioxide in an attempt to extrude sulfur dioxide to give benzothiete also was unsuccessful. The naphthothiete 205, however, was prepared by extrusion of sulfur dioxide from 220 and nitrogen from 221. Thiete 205 also is obtained in 6-8% yield by treatment of 1,8-dehydronaphthalene with carbon disulfide. The unstable thiolactone 211 was formed by a photochemical extrusion of benzaldehyde from 222 and from 222a at 350°C. The benzothietes 209, 223, " and 224 have been... 

The structure of a [4.2.1]propellane derivative prepared in 35-45 % yield similarly to the [4.1.1]homolog from 1-chloroquadricyclane in the presence of anthracene was also determined, again exhibiting the inverted tetrahedron phenomenon ... 

Preparation of anthracene derivatives by ring closure. Anthraquinones... 

Dichloro- and l,l-difluoro-l/7-cyclopropa[b]naphthalcnc (8a and 8b) " and the corresponding 1 //-cyclopropa[b]anthracene derivatives 8c and 8d " were prepared by analogy via cycloaddition of 4,5-dimethylenecyclohexene and 2,3-dimethylene-l,2,3,4-tetrahydro-naphthalene to the respective tetrahalocyclopropenes. The adducts were dehydrogenated with... 

One of the most complex molecules yet prepared by these biomimetic approaches is the x-etetramid (158 Scheme 7). The 3-pyrrolidinoglutaric acid diamide (153) is condensed with two equivalents of the dianion of r-butyl acetoacetate. The putative intermediate (154) undergoes spontaneous cyclization to provide the naphth ene derivative (155). This substance is transformed by a sequence of steps into naph-thalenopyrone (156), which is extended by reaction with an isoxazole dianion. Spontaneous aldolization again occurs, yielding the anthracene derivative (157). Closure of the final ring ensues when (157) is treated with HI. 

The plant excretion chrysarobin is a mixture of various anthracene derivatives and can be chromatographed Just like the synthetic 1,8-dihydroxyanthranol (cignolin, anthralin, dithranol) on silica gel G layers with solvent XII it may be detected in this way in the corresponding preparations [14]. 

Since the adduct of anthracene derivatives is in equilibrium with the reactants, many times it is advantageous to use a large excess of MA to obtain preparative amounts of the product. The equilibrium adduct formation and the effect of excess MA in the anthracene series is shown in Table 4.4. ° Kaplan and Conroy have studied a number of 2-substituted anthracenes. It was shown that the reaction rate, as expected, was enhanced with R = N(CH3)2 and decreased with R = NO2. 

Regulatory Status. Aloe has been approved for food use as a natural flavoring ( 172.510) and is regulated in the United States as a dietary supplement. Dried Aloe vera leaf juice (and preparations) calculated to contain at least 28% hydroxy anthracene derivatives (as anhydrous barbaloin), and A. ferox dried leaf juice (and preparations) calculated to contain at least 18% hydroxy anthracene derivatives (as anhydrous barbaloin), are the subject of a German BGA monograph (blumenthal 1). 

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