Iron Catalyst Alkyne hydration

Anhydrous iron(III) halides catalyse coupling of alkynes and aldehydes.211 Simple terminal alkynes, R CH, react with aldehydes, R2CHO, to give ( ,Z)-1,5-dihalo-1,4-dienes (55). In contrast, non-terminal arylalkynes give ( ,)-o, /3-unsaturated ketones. The catalysts also promote standard Prins cyclization of homoallylic alcohols. Studies of intermediates and of alkyne hydration - together with calculations - all support FeX3 complex formation with alkyne as the activating step. 

For the later transition metals rRhQfPEt ) .] catalysed addition of aniline to norbomene is very slow (25 TO in 12 days). Fragments, derived from BuONO, are added to alkenes leading to oximes and nitrosyis by iron or cobalt catalysts and these are alternative routes for nitrogen inclusion. A short summary of ruthmium catalysed incorporation of R2NCO2 into alkynes covers the latest developments in this area, while alkyne hydration by [RhCl4(H20)2] is proposed to involve a cis-hydroxide addition. ... 

The nse of polysnlfide complexes in catalysis has been discnssed. Two major classes of reactions are apparent (1) hydrogen activation and (2) electron transfers. For example, [CpMo(S)(SH)]2 catalyzes the conversion of nitrobenzene to aniline at room temperature, while (CpMo(S))2S2CH2 catalyzes a number of reactions snch as the conversion of bromoethylbenzene to ethylbenzene and the rednction of acetyl chloride, as well as the rednction of alkynes to the corresponding cw-alkenes. Electron transfer reactions see Electron Transfer in Coordination Compounds) have been studied because of their relevance to biological processes (in, for example, ferrodoxins), and these cluster compounds are dealt with in Iron-Sulfur Proteins. Other studies include the use of metal polysulfide complexes as catalysts for the photolytic reduction of water by THF and copper compounds for the hydration of acetylene to acetaldehyde. ... 

Nolan and coworkers applied cationic gold(l) complexes of N-heterocyclic carbenes at elevated temperatures in the catalytic hydration of terminal and internal alkynes at very low catalyst loadings of 1,000 ppm (0.1%) down to 10 ppm (0.001 %). The thermal stability of the gold(l) carbene complex appears to be critical to achieve those results [123] (Scheme 21b). Iron Iron(III) chloride catalyzes... 

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