Ortho-functionalization of aromatic ketones via manganation. A synthesis of indenols

Synthesis and alkyne-coupling chemistry of cyclomanganated 1- and 3-acetylindoles, 3-formylindole and analogues

“…There is a Mn(CO) 3 group that has remained coordinated to the 3-acetyl group of the indole. It is also 3 -coordinated to an allyl moiety that is part of a methylene-cyclopentadiene group attached at C(2) of the indole.…”

“…Coupling of alkynes with orthomanganated aryl ketones to form 1H-inden-1-ols has been reported by us [1,2] and by Liebeskind's group [3], as have the corresponding alkyne-coupling reactions of orthomanganated N,N-diphenylhydrazones of acetophenone and benzaldehyde to form indenylhydrazines [4]. Cambie et al subsequently used these methods to prepare new steroidrelated compounds using substrates derived from the natural product podocarpic acid [5].…”

“…Because there is renewed interest in the synthesis of this class of polycyclic indole derivative [9] we report more general alkyne-coupling chemistry of 1, its Mn(CO) 2 [P(OMe) 3 ] 2 analogue 2, and the related 2-Mn(CO) 4 derivatives of 3-acetylindole and N-methyl-3-acetylindole (3,4). The report also includes the synthesis of the new cyclomanganated indole derivatives 2, 4, 5a…”

Manganese carbonyl-mediated reactions of azabutadienes with phenylacetylene, methyl acrylate and other unsaturated molecules

“…Several groups have shown that reactions between cyclomanganated aryl ketones or chalcones and alkynes proceed via insertion/cyclisation processes to give novel derivatives [8,13], so the corresponding reaction was investigated here. When a mixture of the azabutadiene 3a, PhCH 2 Mn(CO) 5 and PhC CH (ca 1:1:3) was heated in petroleum spirits a reaction occurred to give a solution with v(CO) peaks indicative of a Mn(CO) 3 group, but shifted ~10 cm -1 to lower frequencies compared with those of the pyrrolinonyl-complex 7.…”

“…Substrates that have been examined include aryl-and hetero-aryl ketones [2] and imines [3], benzylamines [4], triphenylphosphine chalcogenides [5] and triphenylphosphine imines [6]. These complexes undergo a series of interesting reactions involving the Mn-C bond with alkenes [7], alkynes [8], organic isocyanates [9], sulfur dioxide [10] and carbon disulfide [11]. More recently, cyclomanganation studies have been extended beyond aryl substrates to reactions involving , -unsaturated ketones (chalcones) where compounds of the type 2 could be formed [12].…”