Synthesis of Fused‐Ring Indenes by Ruthenium‐Catalyzed Ring‐Closing Metathesis

Abstract

The preparation of new 1,2‐unsymmetrically substituted fused‐ring indenes from dialkenyl precursors by utilization of the ruthenium‐catalyzed ring‐closing metathesis is described. By analogous strategy, 1,3‐substituted fused‐ring indenes with medium‐ring sizes have also been synthesized. For bis(allylsilyl)indene, the formation of a 1,3‐fused ringappears to be prevented by ring strain and a 1,1‐spiro compound is obtained instead due to rearrangement of the substituents. The rearrangement is enabled by the [1,5]‐silatropic shifts operating in silyl‐substituted cyclopentadienyl compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Enantioselective Desymmetrization of 1,2,3-Trisubstituted Metallocenes by Molybdenum-Catalyzed Asymmetric Intraannular Ring-Closing Metathesis

“…In this article, we report extension of the “intraannular” protocol to the molybdenum-catalyzed enantioselective desymmetrization of C s -symmetric ferrocene/ruthenocene derivatives. The substrates for this study are η 5 -(1,2,3-triallylindenyl) complexes 1 , where the two allylic substituents at the 1- and 3-positions in the η 5 -indenyl are enantiotopic to each other . The desymmetrization reaction described in this report provides the nonbridged η 5 -dihydrofluorenyl complexes 2 in excellent enantioselectivity of up to 98% ee (Scheme (c)).…”

Recent Advances in the Synthesis of Indanes and Indenes

“…Synthesis of spirocyclicindane derivative 388 by Ru-catalyzed RCM of amixture of reaction of 1,3-and 1,1-diallylsilylsubstituted indanes 386 and 387. [143] Scheme150. Synthesis of 1-alkylated indene-2-carboxylates 390 by reaction between 1-acetoxy-1H-indene-2-carboxylate 389 and Grignard reagents in the presence of catalyticamountso fLiCuBr 2 .…”

“…As an example, Scheme shows the formation of the spirocyclic derivative 388 by Ru‐catalyzed RCM of a mixture of 1,3‐ and 1,1‐diallylsilylsubstituted indanes 386 and 387 , obtained by lithiation of indene followed by reaction with allyl(chloro)dimethylsilane. Interestingly, the spiro compound was the only RCM product isolated, probably after in situ isomerization of 386 into 387 …”

“… Synthesis of spirocyclic indane derivative 388 by Ru‐catalyzed RCM of a mixture of reaction of 1,3‐ and 1,1‐diallylsilylsubstituted indanes 386 and 387 …”

“…Interestingly,the spiro compound was the only RCM product isolated, probably after in situ isomerization of 386 into 387. [143] Indenyl acetates can be used as suitable allylic substrates for the b-alkylation reactionw itho rganocopper reagents.T hus, the reaction of ethyl 1-acetoxy-1H-indene-2-carboxylate 389 with the organocopper intermediates generated in situ from Grignardr eagents and ac atalytic amount of LiCuBr 2 led to the formation of 1-alkylated indene-2-carboxylates 390 in good yields, as shown in Scheme150. [144] Another interesting transformation was published recently.I t consisted of the thermali somerization of iminolactones 391 (obtained by the reaction between alkyl isocyanides, carbonyl compounds, and acetylenic diesters) into functionalized indenes 392,c arriedo ut in refluxing p-xylene (Scheme 151).…”