A fluorous-tagged linker from which small molecules are released by ring-closing metathesis.

A fluorous-tagged linker for the parallel synthesis of small- and medium-ring and macrocyclic nitrogen heterocycles using ring-closing metathesis is described. The linker was designed such that "cyclization-release" of the cyclic heterocyclic products was coupled with liberation of the active catalyst. The design of the linker was validated using a non-fluorous-tagged model.

Boronate titanium alkylidene reagents for diversity-based synthesis of benzofurans.

[reaction: see text] Novel titanium benzylidenes (Schrock carbenes) bearing an arylboronate group are generated from thioacetals with low valent titanium species, Cp(2)Ti[P(OEt)(3)](2), and alkylidenate Merrifield resin-bound esters to give enol ethers. Treatment with 1% TFA gives 2-substituted (benzo[b]furan-5-yl)boronates, and solid-phase Suzuki cross-coupling gives 2,5-disubstituted benzofurans. Steps in the syntheses of thioacetal substrates include selective lithiation-boronation, hydrolysis of a MOM group without affecting a boronate ester, and cross-coupling with bis(pinacolato)diboron.

Synthesis of 2-substituted benzofurans and indoles using functionalized titanium benzylidene reagents on solid phase.

Titanium(IV) benzylidenes bearing a masked oxygen or nitrogen nucleophile in the ortho position were generated from thioacetals, using low-valent titanocene complex, Cp2Ti[P(OEt)3]2. Methylene acetal, alkyl ether, silyl ether, fluoro, tertiary amino, and N-alkyl, N-benzyl, N-prenyl, and N-silyl tert-butyl carbamate groups were tolerated in the titanium alkylidene reagents (Schrock carbenes). Aryl-chlorine bonds were stable to the titanium benzylidene functionality, but there was poor chemoselectivity for the reduction of the thioacetal in the presence of an aryl chloride.