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A one-pot approach to indolo[2,1-b]quinazolines from indole-3-carbaldehydes through the Dakin oxidation was developed. It was shown that the reaction proceeded through the condensation of indole-3-carbaldehydes with isatoic anhydrides, derived in situ from indole-3-carbaldehydes by the Dakin oxidation, and further oxidation/cyclization steps.  相似文献   
33.
A novel AuICoIII coordination system that is derived from the newly prepared [Co(D ‐nmp)2] ( 1 ; D ‐nmp=N‐methyl‐D ‐penicillaminate) and a gold(I) precursor AuI is reported. Complex 1 acts as a sulfur‐donating metallaligand and reacts with the gold(I) precursor to give [Au2Co2(D ‐nmp)4] ( 2 ), which has an eight‐membered AuI2CoIII2 metallaring. Treatment of 2 with [Au2(dppe)2]2+ (dppe=1,2‐bis(diphenylphosphino)ethane) leads to the formation of [Au4Co2(dppe)2(D ‐nmp)4]2+ ( 3 2+), which consists of an 18‐membered AuI4CoIII2 metallaring that accommodates a tetrahedral anion (BF4, ClO4, ReO4). In solution, the metallaring structure of 3 2+ is readily interconvertible with the nine‐membered AuI2CoIII metallaring structure of [Au2Co(dppe)(D ‐nmp)2]+ ( 4 +); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au S and Au P bonds, which is essential for metallaring expansion and contraction.  相似文献   
34.
The results of this study show that disilathiane is an effective mediator in the synthesis of alkyl aryl sulfides with disulfides and alkyl carboxylates. Mechanistic studies suggest that disilathiane promotes cleavage of the sulfur–sulfur bond of disulfides to generate thiosilane as a key intermediate. Diselenides were also applicable to this transformation to produce the corresponding selenides.  相似文献   
35.
The silaboration of [1.1.1]propellane enables direct introduction of B and Si functional groups onto the bicyclo[1.1.1]pentane (BCP) scaffold in high yield under mild, additive‐free conditions. The silaborated BCP can be obtained on a gram‐scale in a single step without the need for column‐chromatographic purification, and is storable and easy to handle, providing a versatile synthetic intermediate for BCP derivatives. We also describe various conversions of the C?B/C?Si bonds on the BCP scaffold, including development of a modified Suzuki–Miyaura cross‐coupling reaction at the highly sterically hindered bridgehead sp3 carbon center of the BCP skeleton using a combination of highly activated BCP boronic esters, copper(I) oxide, and a PdCl2(dppf) catalyst system.  相似文献   
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The electron transfer quenching of 2-aminopurine by guanine and 7-deazaguanine was investigated in B- and Z-DNA, and an increase in the fluorescence intensity of 2-aminopurine upon B- to Z-DNA transition was demonstrated.  相似文献   
39.
Ice crystallisation in crosslinked dextran (Sephadex) gels was studied by the method of two-dimensional X-ray diffraction (XRD) in combination with the simultaneous measurement of differential scanning calorimetry (DSC). With a Sephadex G25 gel where an exotherm due to ice crystallisation is observed in the DSC rewarming trace, it was indicated by the XRD pattern that small ice crystals less than approximately 10 microns in diameter are readily formed during freezing, and that the endothermic trend prior to the exotherm is not due to the glass transition but due to the melting of the small ice crystals. Moreover, the diffraction pattern observed with frozen Sephadex gels depended on the density of crosslink indicating that ice crystals of different size and dimension are formed in the gels.  相似文献   
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