The regiospecific cobalt carbonyl catalyzed synthesis of dienones and trienones by phase transfer catalysis

C3‐Thioester/‐Ester Substituted Linear Dienones: A Pluripotent Molecular Platform for Diversification via Cascade Pericyclic Reactions

“…But the expected product was not obtained when a dienone ( 1 z ) bearing C 3 −COMe group was either stirred at room temperature or heated at 40 °C to 50 °C or higher temperature, possibly due to the presence of an additional C 3 ‐keto group which leads to undesired side reactions. Moreover, the dimerization of substrates 1 aa , 1 ab , or 1 ac lacking any substitution at the C 3 ‐position was completely inhibited, which further supports the substituent‐driven acceleration effect caused by the C 3 ‐thioester/‐ester group…”

Carbonylation and Decarbonylation Reactions

“…By using a phase transfer method increased yields can be obtained under milder conditions (1 bar, 25°C). 29 The reaction is highly stereo-and regio-specific since the acyl group is normally added to the least-substituted carbon atom of the least-substituted double bond, with exclusive formation of the trans-acyldiene. The (acyl-'IT-allyl)cobalt complex (5), an intermediate in this reaction, can also be reacted with stabilized carbanions resulting in alkylation of the unsubstituted 'IT-allyl terminus to give the product (6).…”

“…I 13 Under these conditions none of the bridgehead alkene is obtained, but it is assumed that this is an intermediate in the reaction. (29) COCI (30) …”

Cobalt-Catalyzed Carbonylative Cross-Coupling of Alkyl Tosylates and Dienes: Stereospecific Synthesis of Dienones at Low Pressure

“…We were intrigued by prior reports demonstrating cobalt-catalyzed couplings with dienes, albeit with primary or activated electrophiles. 7 Herein, we report a catalytic, stereospecific carbonylative cross coupling of alkyl electrophiles using an easily accessed anionic cobalt catalyst. This mild, catalytic process enables the stereoselective synthesis of valuable dienones from chiral, non-racemic secondary alkyl tosylates and dienes in a convergent manner.…”

“…The inorganic base Cs 2 CO 3 was inferior to the organic base TMP and completely racemized the product (entry 8). Reaction in the absence of ambient light proceeded with only a slight decrease in yield and enantiospecificity (78% 1 H NMR yield, 90% es , entry 9), 7d and no reaction occurred in the absence of catalyst (entry 10).…”