Carbonyl compounds intramolecular arylation

In certain cases, Michael reactions can take place under acidic conditions. Michael-type addition of radicals to conjugated carbonyl compounds is also known.Radical addition can be catalyzed by Yb(OTf)3, but radicals add under standard conditions as well, even intramolecularly. Electrochemical-initiated Michael additions are known, and aryl halides add in the presence of NiBr2. Michael reactions are sometimes applied to substrates of the type C=C—Z, where the co-products are conjugated systems of the type C=C—Indeed, because of the greater susceptibility of triple bonds to nucleophilic attack, it is even possible for nonactivated alkynes (e.g., acetylene), to be substrates in this... 

An extensive review of the hetero-Diels-Alder reactions of 1-oxabuta-1,3-dienes has been published. Ab initio calculations of the Diels-Alder reactions of prop-2-enethial with a number of dienophiles show that the transition states of all the reactions are similar and synchronous.Thio- and seleno-carbonyl compounds behave as superdienophiles in Diels-Alder reactions with cyclic and aryl-, methyl-, or methoxy-substituted open-chain buta-1,3-dienes.The intramolecular hetero-Diels-Alder reactions of 4-benzylidine-3-oxo[l,3]oxathiolan-5-ones (100) produce cycloadducts (101) and (102) in high yield and excellent endo/exo-selectivity (Scheme 39). A density functional theoretical study of the hetero-Diels-Alder reaction between butadiene and acrolein indicates that the endo s-cis is the most stable transition structure in both catalysed and uncatalysed reactions.The formation and use of amino acid-derived chiral acylnitroso hetero-Diels-Alder reactions in organic synthesis has been reviewed. The 4 + 2-cycloadditions of A-acylthioformamides as dienophiles have been reviewed. ... 

Other solid-phase preparations of carbonyl compounds include the hydrolysis of acetals (Table 12.4), inter- [52] and intramolecular Pauson-Khand reactions, the isomerization of allyl alcohols, and the a-alkylation and a-arylation of other ketones. Tietze reported the generation of acetoacetyl dianions on cross-linked polystyrene and their selective alkylation at C-4 (Entry 6, Table 12.4). The use of weaker bases resulted in single or twofold alkylation at C-2 [53]. 

Electrophilic ring closure of aryl-substituted compounds such as alkenes, halides, alcohols, and carbonyl compounds called cyclialkylation can be induced by conventional Friedel-Crafts catalysts309 and by superacids. Examples are also known in which an intermolecular alkylation step is followed by intramolecular alkylation of the intermediate to furnish a cyclic product. 

The first cyclisations to be put to synthetic use were those of aryl lithiums onto carbonyl compounds, imines and epoxides. These are known as Parham cyclisations , and the method for transforming an aryl bromide to an aryllithium the Parham protocol , after W. E. Parham, who developed the reaction. We will survey the use of Parham cyclisations in synthesis, before assessing intramolecular attack of other electrophiles. The most important of these are the alkenes, and the usefulness of anionic cyclisations onto unactivated double bonds compares very favourably with radical cyclisations, particularly with regard to stereochemical control. 

Intramolecular Condensation of Substituted Aryl Carbonyl Compounds 843... 

The course of the intramolecular photoreaction of carbonyl compounds with electron-rich alkenyl- or aryl-substituents in the side-chain is dictated essentially by the thermodynamics of the electron-transfer step. This relationship has been intensively studied for phthalimides. When AG°et is positive, [n 2 + 2] cycloaddition reactions were observed with alkenyl substituents and classical Norrish II chemistry for aryl-substituted substrates. When AG°et was negative, electron transfer prod-... 

The organozinc carbenoids generated from aryl and a, -unsaturated carbonyl compounds with zinc and l,2-bis(chlorodimethylsilyl)ethane can be trapped intramolecularly to give cyclo-... 

One of the major problems encountered in this synthesis is the difficulty of obtaining the starting materials (either the a-aminocarbonyl compounds or their acylated derivatives). The former may be prepared by Neber rearrangement of ketoxime tosylates with a base such as ethoxide or pyridine.46 a-Acylamino carbonyl compounds can be prepared directly by the reductive acetylation of oximino ketones.28 38 Balaban and his collaborators47-60 have developed an excellent method for the synthesis of a-acylamino ketones (5). They are obtained in yields of 50-90% by the reaction of azlactones (2-aryl-5-oxazolone, 4) with aromatic hydrocarbons in the presence of aluminum chloride under Friedel-Crafts conditions the reaction may proceed either intermolecularly or intramolecularly. 

The direct intermolecular a-arylation of relatively less acidic ketones with aryl halides, which proceeds by mechanism B, was reported concurrently in 1997 by the groups of Miura, Buchwald, and Hartwig [35-37]. The intramolecular version was also described by Muratake and coworkers in the same year [38,39], while some intermolecular vinylation reaction had been reported [40, 41]. Taking advantage of this, the reaction of carbonyl compounds and related substrates has been studied extensively. Now a variety of ketones are known to be arylated by using appropriate ligands and bases [42-46]. The reaction usually takes place at a less hindered a position (Eqs. 5-7) [19,20]. 

Biaryl structures are found in a wide range of important compounds, including natural products and organic functional materials [8,80,81]. One of the most common and useful methods for preparing biaryls is the palladium-catalyzed coupling of aryl halides with arylmetals (Scheme 1, mechanism A). On the other hand, aryl halides have been known to couple directly with aromatic compounds as formal nucleophiles under palladium catalysis. While the intramolecular cases are particularly effective, certain functionalized aromatic compounds such as phenols and aromatic carbonyl compounds, as well as... 

By the reaction of a,-unsaturated carbonyl compounds with the dibromide 55, cyclization occurs by a-arylation, followed by intramolecular Mizoroki-Heck reaction. For example, reaction of verbenone (61) with 55 using PPh3 generates 62 by y-arylation of 61, and subsequent intramolecular Mizoroki-Heck reaction affords the indane 63. The benzocyclobutane 67 was obtained unexpectedly... 

Inter-Intra Tandem Processes Involving Pd-Catalyzed a-Arylation of Carbonyl Compounds with 1,2-Dibromoarenes. 1,2-Dibromoarenes have been shown to undergo Pd-catalyzed inter-intra tandem processes leading to the formation of cyclic compounds, as summarized in Scheme 28. In some examples, however, the cyclization process itself does not actually involve Pd-catalyzed a-arylation. It instead involves either an interesting diaryl ether formation (Sect, in.3.3) or intramolecular Heck reaction (Sect. IV.2.2). 

Different from the hydroxyalkylation reactions using carbonyl compounds as substrates, Nicolaou s and Macmillan s groups developed independently the intramolecular asymmetric Friedel-Crafts-type a-arylation of aldehydes with electron-enriched arenes based on the SOMO activation strategy. Using chiral imidazolidione as catalyst, a series of cyclic aldehydes were obtained in good yields and enantioselectivities with cerium ammonium nitrate (CAN) as single electron transfer oxidant [46]. 

---