7-Silylcycloheptatrienes and Analogues: Reactivity and Selectivity in Cascade Processes
摘要:
7-Silyl- and 7-silylmethylcycloheptatrienes react with acylnitroso reagents at room temperature to provide the corresponding silyl- and silymethylnorcaradiene cycloadducts. Depending on the reaction conditions, 7-silylmethylcycloheptatriene was also shown to provide, through cascade processes, functionalized cyclohexa-1,3-dienes or bicyclic synthons, incorporating one and two amino groups, respectively, that may be elaborated further, for instance, into sugar mimics.
polar medium, functionalized cyclohexa‐1,3‐dienes 7 a–b and bicyclic compounds 13 a–b were instead generated, incorporating one or two amino groups. Similar behavior was observed by using other dienophiles, including triazolinedione, but also activated aldehydes and ketones. A tentative mechanism has been proposed to rationalize the formation of both classes of products that relies on a domino process
7-Silyl- and 7-silylmethylcycloheptatrienes react with acylnitroso reagents at room temperature to provide the corresponding silyl- and silymethylnorcaradiene cycloadducts. Depending on the reaction conditions, 7-silylmethylcycloheptatriene was also shown to provide, through cascade processes, functionalized cyclohexa-1,3-dienes or bicyclic synthons, incorporating one and two amino groups, respectively, that may be elaborated further, for instance, into sugar mimics.
Desymmetrization of 7-dimethylphenylsilylcycloheptatriene. Towards the synthesis of new aminocycloheptitols
Desymmetrization of 7-silylcycloheptatriene through consecutive dihydroxylation and acyl-nitroso cycloaddition of the resulting diene moiety is described. Dihydroxylation occurred anti relative to the resident silicon group in line with previous observations made in the cyclohexadiene series. In contrast, the subsequent acyl-nitroso cycloaddition occurred with poor regiocontrol but good level of diastereocontrol syn to the bulky silyl substituent. The resulting cycloadducts were then elaborated further to provide a straightforward entry toward aminocycloheptitols in ten steps from commercially available tropylium salts.