中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 1,5-dimethoxy-2-(prop-1'-enyl)anthraquinone | 240402-96-4 | C19H16O4 | 308.334 |
—— | 1-hydroxy-2-(prop-2'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 113681-17-7 | C20H16O4 | 320.345 |
—— | 1-hydroxy-2-(prop-1'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 240402-91-9 | C20H16O4 | 320.345 |
—— | 1-methoxy-2-(prop-2'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 162307-85-9 | C21H18O4 | 334.372 |
—— | 1-methoxy-2-(prop-1'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 240402-79-3 | C21H18O4 | 334.372 |
—— | 1-benzyloxy-2-(prop-2'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 240403-05-8 | C27H22O4 | 410.469 |
—— | 1-benzyloxy-2-(prop-1'-enyl)-5-(prop-2''-enyloxy)anthraquinone | 240403-06-9 | C27H22O4 | 410.469 |
Syntheses of C2 anthraquinone aldehydes from the commercially availableanthraru¯n (1) have been investigated. A synthesis of the keto aldehyde(2) in nine steps and 73% overall yield was achieved. Syntheses of (2)exploiting selective oxidations of either a C-boundallyl group by Wacker oxidation to introduce the methyl keto functionality orof a C-bound prop-1-enyl moiety by dihydroxylation andoxidative cleavage to generate the C2 formyl group were also developed. Thealdehyde (27) was synthesized in seven steps and in 81% overall yieldfrom (1), and syntheses of the phenolic aldehydes (33), (34), and (35), the C1benzyloxy aldehyde (36) and the anthracene aldehyde (37) were also developed.
(+)-Bis[3-(heptafluorobutyryl)camphorato]oxovanadium(IV) [(+)-VO(hfc)2] (2) is an effective catalyst for the hetero-Diels-Alder reaction of a variety of anthraquinone aldehydes and silyloxy dienes giving high yields of cycloadducts. The reactions all proceed with strict endo topology giving rise to cis products; this indicates that they follow a similar mechanistic pathway to that proposed by Danishefsky for reactions catalysed by the europium complexes Eu(fod)3 and Eu(hfc)3. Reactions employing the dimethoxy aldehydes (3) and (4) and the phenolic aldehydes (5) and (6) proceed with only modest degrees of enantioselection. Reaction with the benzyloxy aldehyde (7) proceeds with significantly reduced enantioselectivity indicating that the nature of a substituent at C1 can have a significant effect. Enantioselectivity is generally higher for reactions at low temperature and when toluene rather than dichloromethane is used as solvent. The cycloadduct (24) has been elaborated to the anthracene C-glycoside (28) of known configuration, thereby establishing that the hetero-Diels-Alder reaction favours formation of the 2′R,6′R enantiomer of (24). This enantiofacial selectivity has been correlated with the sense of anisochrony observed in the 1H n.m.r. spectrum of the ketone (17), a derivative of (24), in the presence of the solvating agent (S)-(+)-trifluoroanthrylethanol [(S)-(+)-TFAE]. The enone (21) has been elaborated to the anthraquinone olivose C-glycoside (33), a synthesis demonstrating the utility of hetero-Diels-Alder reactions involving silyloxy dienes with terminal silyloxy or methyl substituents for such syntheses.