D-Tetralones

Ethylenediamine, complexes with chro-mium(ll) salts, 52,62 Ethyl diazoacetate, as source of car-bethoxycarbene, 50,94 Ethylene, with p-methoxyphenylacetyl chloride and aluminum chloride to give 6-methoxy-d-tetralone, 51,... 

Johnson has developed two linear approaches to synthesize the C-nor-D-homosteroid skeleton (Scheme 2.2). In his first approach [21], tetralone 19, obtained from reduction of 2,5-dimethoxynaphthalene, was used as the source of the C,D-rings. The B- and A-rings were constructed by sequential Robinson annulations (19 —> 20 —> 21). The Cl 1,12 olefin was then introduced to provide 22. Ozonolysis of 22 followed by an aldol reaction of the resulting dialdehyde gave 23. Subsequent deformylation and deoxygenation afforded the cyclopamine skeleton 24. 

The generality of such intermolecular [D, A] complexes is shown in Fig. lc by the exposure of a colorless solution of a-tetralone enol silyl ether to different... 

When a-tetralone enol silyl ether in dichloromethane is mixed with an equivalent of tetranitromethane (TNM) at room temperature, the solution immediately takes on a bright red coloration owing to formation of the characteristic [D, A] complex37 (equation 12). 

For gas chromatography analysis, samples were spiked with 2-methyl-naphthalene as an internal standard. Samples were analyzed using a Shimadzu GC-17A series gas chromatograph equipped with RTX-5 column, 15 m (length) 0.25 mm (i.d.) and 0.25 pm (film thickness). The initial column temperature was 70 °C and temperature was increased at 20 °C min 300 °C, and column temperature was held for 13 min. Retention times R naphthalene, 3.2 min 2-methyl-naphthalene, internal standard, 4.09 min 1-tetralone, 4.7 min menadione, 5.68 min 1-naphthol, 5.7 min 4-hydroxy-1-tetralone, 6.1 min and 2-methy 1-4-hydroxy-1-tetralone, 6.18,6.27,6.3 and 6.4 min. 

Anm. wahrend d. Korr. 6-Methoxy-l-tetralon, in dem dor clcktronische Eliekt des Aromaten dem in (7) vergleichbar ist, liefert jedoch iibcrvvicgend das Laktam mit CO am Bcnzolring [analog (14)] Evans, D. u. I. M. Lockhart, The Schmidt reaction with aromatic ketones. J. Cheni. Soc. [London] 1965, 4806. 

C. Regeneration of p-telralone. Fifty grams (0.20 mole) of /8-tetralone bisulfite addition product is suspended in 250 ml. of water, and 75 g. (0.6 mole) of sodium carbonate monohydrate is added. At this point the pH of the solution is approximately 10. The mixture is extracted with five 100-ml. portions of ether (Note 8). The combined extract is washed with 100 ml. of 10% hydrochloric acid, then with 100-ml. portions of water until the washings are neutral to litmus, and is dried over anhydrous magnesium sulfate. The ether is removed by distillation, and the residue is distilled from a Claisen flask under reduced pressure, preferably in a nitrogen atmosphere. The pure /3-tetralone is obtained as a colorless distillate b.p. 70-71°/0.25 mm. (92-94°/1.8 mm., 114-116°/4.5 mm.) d 1.5594. The yield is 17-21 g. (40-50% based on /3-naphthyl ethyl ether). 

The catalytical decomposition of iodonium ylides is especially useful as a method of cyclization via intramolecular cycloaddition or bond insertion [146 -148]. Several representative examples of these cyclizations are shown in Scheme 73. Specifically, the intramolecular cyclopropanation of ylide 203 leading to product 204 was used in the synthesis of the 3,5-cyclovitamin D ring A synthon [146]. The copper(I) catalyzed decomposition of phenyliodonium ylides 205 affords the corresponding substituted tetralones 206 in good preparative yields [147]. Under similar conditions,iodonium ylides 207 undergo regio-and stereoselective intramolecular cyclopropanation to form the key bicy-clo[3.1.0]hexane intermediates 208 for prostaglandin synthesis [148]. 

The starting materials for the preparation of naphtho[l,2-d]-l,3-tellurazoles are a-tetralones, tellurium dioxide, hydroxylamine, and hydrochloric acid1,2. 

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