Organomanganese halides

Selective addition to aldehydes. Organomanganese halides add to aldehydes selectively in the presence of ketones. This is true for RMnI, RMnBr, prepared from RLi and MnBr2, and for RMnCl, prepared from RLi or RMnX and MnCl2. ... 

Organomanganese halides are reported to undergo synthetically useful... 

R MnCI is mild enough that chiral a-acyloxy ketones can be prepared. Such organomanganese halides can be directly made from the halides and Rieke manganese. ... 

As for most organometallics derived from a transition metal, organomanganese halides are prepared by a metal-metal exchange reaction from organolithium or organomagnesium compounds in ether or in THF [3]. 

In ether, organomanganese halides readily add to aldehydes and ketones at 0 °C, affording the corresponding alcohols in high yields. However, they react neither with nitriles nor with less reactive carbonyl compounds such as amides and esters, except with formates [11] (Scheme 13.5). 

Contrary to organolithium or organomagnesium compounds, organomanganese halides add chemoselectively to aldehydes in the presence of ketones (Scheme 13.6) [12]. The scope of the reaction is very large since n- or s-alkyl, alkenyl, aryl and alkynylmanganese halides are always completely aldehyde-selective at room temperature, in ether as in THF. 

Interestingly, in the case of the a,/3-ethylenic aldehydes, organomanganese halides allow the 1,4-addition or 1,2-addition product to be obtained selectively by working with or without copper salts (Scheme 13.42) [37]. 

The chemoselectivity of this reaction deserves to be emphasized. Thus, in the presence of 3% iron acetyacetonate, organomanganese halides react with o)-ketoalke-nyl chloride to give exclusively the coupling product (Scheme 13.51). 

Ketones. Organomanganese reagents are formed by reaction of various halides (e.g., benzyl, aryl, heteroaryP) with Rieke Mn, which is prepared by reduction of manganese(II) halides with lithium naphthalenide in THF. Such reagents react with acid chlorides to afford ketones. 

Organomanganese(II) halides react with phosgene in diethyl ether (-40 - +20 C) in a predictable manner [323] ... 

Direct Formation of Aryl-, Alkyl-, and Vinylmanganese Halides via Oxidative Addition 307 Table 8.1 Formation and coupling reactions of organomanganese bromides. 

Benzylic Manganese Halides, Sulfonates, and Phosphates 329 Table 8.12 Preparation of organomanganese tosylates and their coupling reaction. 

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