An Improved Catalyst for Ring-Closing Alkyne Metathesis Based on Molybdenum Hexacarbonyl/2-Fluorophenol

Abstract

[reaction: see text] An improved "instant" catalyst for ring-closing alkyne metathesis reaction is described. Catalyst formed in situ from molybdenum hexacarbonyl and 2-fluorophenol can be used without exclusion of air and moisture and shows high activity in metathesis of functionalized diynes. This system allows cyclization of substrates which were incompatible with previously known Mo(CO)(6)/phenol catalysts.

Alkyne Metathesis: Catalysts and Synthetic Applications

“…Such a catalyst system was initially discovered by Mortreux, [7,52] and later improved and widely used by Bunz, [4,53,54] Mori, [55] Fürstner [3] and more recently Grela. [56,57] This "instant" method is attractive because all the ingredients are inexpensive, commercially available and stable "off the shelf" reagents can be used directly without the rigorous purifications and an inert atmosphere. [58] However, this catalytic system shows poor compatibility with some heteroatom functional groups, such as esters, aldehydes, pyridines etc.…”

A study of molybdenum catalysts in the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene

“…All three catalyst precursors show similar activity and produce PPEs 2 of similar P n . How do 3-5 compare with Mo(CO) 6 [2]? When using small amounts of reactants ($0.5 mmol of 1 and co-catalyst, 5-10 mol% of catalyst), polymer formation was slower when using Mo(CO) 6 to obtain reproducible results.…”

“…How do 3-5 compare with Mo(CO) 6 [2]? When using small amounts of reactants ($0.5 mmol of 1 and co-catalyst, 5-10 mol% of catalyst), polymer formation was slower when using Mo(CO) 6 to obtain reproducible results. The cause for these inconsistencies may be the high volatility of the molybdenum hexacarbonyl.…”

“…Other molybdenum complexes perform alkyne metathesis [3] as well, but there have been no systematic investigations in the effectiveness of these catalysts to form 2. We compare the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene (1) using: (a) (C@C) n Mo(CO) 6 À n (3)(4)(5) [3], (b) MoO 2 (acac) 2 / nAlEt 3 (6) [3] and (c) Mo(CO)(tolane) 3 (7) [4,5] (See Scheme 1).…”

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…RCAM (e.g. conversion of 930 to 931) was also reported using a similar system that employs 2-fluorophenol as a substitute for 2-chlorophenol [651]. Compound 936 was made through either RCM or RCAM [652].…”