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[求助]
(有机化学)求翻译~~金币嫌少可追加~~高手闲暇时光帮下忙哦~~~
Free N–H indoles can also be obtained from 2-alkynyltrifluoroacetanilides in the presence of CuI and 1,2-trans-cyclohexanediamine or PPh3 (Scheme 4).
As observedwith the related palladium-catalyzed synthesis of indoles,thetrifluoroacetamido substituent plays a crucial role in promoting
this transformation. Under the same conditions, moderate yields
were obtained with 2-alkynylanilines or with the corresponding
acetamido derivatives. Furthermore, the trifluoroacetamido group
provides the additional advantage of being readily cleaved (the
amide bond is broken during the reaction or/and the work-up)
so as to allow for the formation of the free N–H pyrrole nuclei,
avoiding troublesome and time-consuming deprotecting steps.The copper-catalyzed intramolecular hydroamination protocol
has been exploited to develop microwave-assisted solid-phase syn-
theses of indoles. Under microwave irradiation,N-acyl-2-alkyl-
5-arenesulfamoylindoles have been obtained from resin-bound
2-alkynylanilides, after cleavage from the resin with trifluoroacetic
acid in dichloromethane (Scheme 5).More recently, a linker containing a tripeptide unit with dual
functions for anchoring the 2-alkynylanilide fragment onto a solid
support and for promoting a copper-mediated heterocyclization
has been developed (Scheme 6).
N-Acyl chains contained in
the indole derivative after cleavage can be easily removed upon
exposure to pyrrolidine, which results in an indirect traceless20
solid-phase synthesis.
The effect of the tripeptide unit on the cyclization step has been
explained by a metal-catching (via formation of a Cu(II) complex
through the amide carbonyl oxygen donors) and activation
mechanism (via chelation of the copper ion with the neighboring
alkyne fragment) (Fig. 1). |
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