Carbon nucleophiles enones

Tamttra and coworkers have reported a related sttbsdntdon reacdon cyclic ct-fnitroalkyl enones undergo regioselecdve sttbsdnttion of the nitro group by sulfinate ion, amino, and carbon nucleophiles fEq. 7.23. Several reacdon pathways are envisioned for this useful... 

The first organocatalyzed conjugate addition of a-substituted p-ketoester to a,P-unsaturated ketones was presented by Deng et al. [42] (Scheme 3). Although traditional Cinchona alkaloids were efficient catalysts for conjugate addition of carbon nucleophiles to nitroalkenes and sulfones, replacement of the C(9)-OH with an ester group (Q-7b) showed great improvement in stereoselectivity. The reaction is applicable to a variety of cyclic and acyclic enones (16,18). 

Cyanide ion acts as a carbon nucleophile in the conjugate addition reaction. An alcoholic solution of potassium or sodium cyanide is suitable for simple enones. 

Reaction of the ambidentate complex 1 with carbon nucleophiles results in exclusive 1,4-addition (Michael addition) to the enone-like acyl ligand no products of 1,2-addition of the nucleophile are observed (see also Houben-Weyl, Volume 13/9 a, p 416)38 39. 

Synthetic applications of the /1-pathway include conversions of the TIPS allylic azides to enones with tetrabutylammonium fluoride, ionization of the C-N3 bond with alkylaluminum reagents and capture of the TIPS enonium ions with carbon nucleophiles, and development of a procedure for y-lactamization [15-17]. Allylic azidonations of TIPS enol ethers have also been incorporated into syntheses of (+)-pancratistatin [18,19] and the core structure of lycorane [20]. 

Structures I and II differ only in the lactonic C-O bond. This seemingly simple transformation conceals complications derived from the oxidative process involved in the formation of this bond. Necessarily, the oxidant must be an external agent since the enone II does not show the traces (reduced fragments) that are always produced during any intramolecular redox operation. This oxidizing agent in all probability is bromine. In fact, one could predict, in the absence of any further evidence, that the reaction mechanism must proceed by way of an allylic bromination at the 7 carbon of enone I, which would provide the required functionalization for an intramolecular nucleophilic displacement of bromide by the carboxylate anion in a second step. This is shown in structure... 

Ordinary carbon nucleophiles such as cyanide or Grignard reagents or organolithium compounds fit the patterns we have described already. They usually give the more stable product by 5 2 or 5 2 reactions depending on the starting material. If we use copper compounds, there is a tendency— no more than that—to favour the 5 2 reaction. You will recall that copper(l) was the metal we used to ensure conjugate addition to enones (Chapter 10) and its use in Sn2 reactions is obviously related. 

Various other tricyclic cyclopropane systems with the nortricyclene skeleton, e.g. 27-29, can be obtained via alkoxypalladation of norbornadiene and subsequent reaction with enones, cuprates, or other carbon nucleophiles. ... 

Enones derived from carbonyl condensations can undergo further carbon-carbon bond-forming reactions on addition of carbon nucleophiles. When the nucleophile adds at the 4-position (rather than the 2-position) of the enone, this is known as the Michael reaction. 

Not only simple, unactivated olefins but also a,P-unsaturated carbonyl compounds undergo gold-catalyzed addition reactions. Electron-rich arenes or heteroarenes (e.g., indoles) are suitable carbon nucleophiles for these Michael additions. For the 1,4-addition of indoles to enones, enals, and related Michael acceptors, simple gold(III) catalysts like NaAuCl4-2 or AuCU can be used... 

Subsequent studies demonstrated that the asymmetric Michael addition of trisubstituted carbon nucleophiles promoted by 6 -demethylated Cinchona alkaloids (CPD, CPN, RO-CPD and RO-CPN) could be efficiently achieved using a,p-unsaturated sulfones, enones and enals as Michael acceptors in a highly enantioselective and diastereoselective fashion. 

Carbon nucleophiles Alkyl-substituted nitrogen heteroaromatics HetAr-Me, such as a-picoline, have been shown to add to enones R CH=CHCOR and a,)3-unsaturated A-acylpyrroles in a reaction catalysed by (TfO)3Sc or (TfO)3Y to afford Michael adducts HetArCH2-CH(R )CH2COR as a result of formal activation of the benzylic C-H bond. ... 

Additions of carbon nucleophiles to enones and the consequent synthesis of C-glycosyl compounds are noted in Chapter 3,... 

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