Spiro-2-tetralones

Simultaneous B Ring Formation/C Ring Expansion Starting from Spiro-2-tetralones... 

The fixed geometry of a, 3-unsaturated ketones in the S-cis form, as observed in arylidene alkanones, influences their reactivity. For example, the reaction of arylhydrazines with 3,5-diarylidene-4-piperidones, 2-arylidene-l-tetralones, 2,6-diarylidenecyclohexanones and 2-arylideneindan-l,3-diones requires stronger conditions than for the case of their noncyclic analogues [76, 77, 78, 79, 80, 81, 82, 83, 84]. However, arylidene derivatives of cyclohexanone, 1-indanone, 4-chromanone, 4-thiochromanone and TV-methyl-4-piperidone hydrochloride react with hydrazines more easily [85,86,87,88], It is interesting to note that the more complicated and sterically hindered unsaturated ketones of the spiro type 64 react with hydrazine and phenylhydrazine very easily in the presence of piperidine, leading to pyrazoles 65 in high yields [89] (Scheme 2.16). 

The structure and absolute stereochemistry of hinesol (282) has now been firmly established by an unequivocal synthesis which involved the tricyclic dienone (329) prepared from 6-methoxy-l-tetralone. Treatment of the dienone with lithium dimethylcopper gave a mixture of syn and anti enones (330). By a series of stereoselective reactions this compound was converted to the diol (331) whose mono-mesylate underwent a base-induced cleavage to give the spiro[4,5]-ketone (332). Elaboration of this ketone to hinesol was accomplished along... 

Similarly, the nitrones (148) have been reacted with both cyclic a-ketosulfene (160) and (161), generated in situ from 2-chlorosulfonylindanone and 2-chlorosulfonyl-l-tetralone by treatment with triethylamine, to give the rearranged spiro compounds (162) and (164), l,2,5-benzoxathiazepine-3-spiro-2 -indanones and -2 -(r-tetralones), together with small amounts of the tetracyclic 1,2,5-benzoxathiazepines (163) and (165), respectively (Scheme 25) <76JCK 2438>. 

The Hantzsch thiazole synthesis from thioamides and a-halogeno-ketones has been applied to iVAr-(dimethyl)dithio-oxamide to give 2-(dimethylthio-carbamoyl)thiazoles, but in some cases it took another course. Thus, 1-alkylthiocarbamoyl-l-cyanoacetophenones (91) react with bromo-ketones with elimination of alkylamine, giving 2-methylidene-l,3-oxathioles (92). The thio-anilide of acetoacetic acid reacts with 2-bromo-l-tetralone to give the spiro-... 

This general method has been applied in particular to the case where Rj = CH3 and R2 = CHjCgHj. Vast synthetic possibilities are thus available for the preparation in high yields of indanone and tetralone derivatives disubstituted in the 2 position. These arene complexes (e.g., LXVII) are also of considerable use in annulation reactions (Jaouen and Meyer, 1976) and in the synthesis of spiro compounds (Meyer et al, 1977). 

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