Phenylseleninic anhydride

The phenanthrene 1,2- and 3,4-diones are synthetically accessible from the related 8 phenols. Oxidation of 2-phenanthrol with either Fremy s salt ((KS0 )2N0) or phenylseleninic anhydride gave phenanthrene 1,2-dione directly (55). Unexpectedly, oxidation of 3-phenanthrol with (KSOg NO yielded 2,2-dihydroxybenz(e)indan-l,3-d-ione (Figure 10). However, phenanthrene 3,4-dione was readily obtained from 3-phenanthrol by Fieser s method entailing diazonium coupling, reduction, and oxidation of the resulting 4-amino-3-phen-anthrol with chromic acid (56). 

Anthracene is noncarcinogenic and is structurally incapable of forming a bay region diol epoxide. Anthracene 1,2-dihydrodiol is most conveniently synthesized from 2-anthranol by oxidation with phenylseleninic anhydride to anthracene 1,2-dione (55) followed by reduction with NaBH in ethanol (22) or LiAlH (55). Anthracene 1,2-dihydrodiol has also been synthesized via the Prdvost reaction route... 

The final phase of the synthesis is introduction of the C-9 oxygen by phenylseleninic anhydride (step H-9). 

Other workers have concentrated on the introduction of functionality into ring C of tabersonine (78). Danieli et al. (252) introduced the 17-hydroxy group by oxidation of tabersonine by means of phenylseleninic anhydride. Presumably, the Va,17-didehydrotabersonine initially produced suffers nucleophilic attack by water during workup, the stereochemistry of attack being controlled by the adjacent ethyl group. Oxidation of the product, 377, at C-16 by means of peracid also proceeds preferentially at the /3-face to give the V-oxide 378 of the desired diol. Reductive methylation and acetylation then complete the partial synthesis of vindorosine (43) (Scheme 24) (252). 

The synthesis of 3-oxovincadifformine ethyl ester (589) by Danieli et al. (345) also proceeds via thermal cyclization of an appropriate 3-oxosecodine derivative, which in this case was generated by oxidation of the lactam 590 by means of phenylseleninic anhydride (Scheme 76). 

The reaction of Tf20 with phenylseleninic anhydride and diphenyl diselenide directly affords phenylselenenyl triflate (eq 89). This procedure is a convenient alternative to the preparation of phenylselenenyl triflate from light sensitive AgOTf and moisture sensitive PhSeCl. 

Pd(II)Cl2 and trimethylsilyl trifluoromethanesulphonate as alternative catalysts plus 1,4-additions to the aza-dienes were also described. Furthermore, it has been shown that dehydrogenation of secondary amines with phenylseleninic anhydride (or the acid) can... 

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