Ketones, cyclic => diketones

NHC-promoted enolate formation from an enal, followed by a desymmetrising aldol event to generate P-lactones and loss of CO, has been exploited by Scheidt and co-workers to generate functionalised cyclopentenes 240 in high ee from enal substrates 238 (Scheme 12.52) [94]. Interestingly, the use of alkyl ketones in this reaction manifold allows the isolation of the p-lactone intermediates with acyclic diketones, P-lactones 239 are formed with the R group anti- to the tertiary alkox-ide, while with cyclic diketones the P-lactone products have the R group with a syn relationship to the alkoxide [95]. 

KETENE, feef-butylcyano-, 55, 32 37, 38 Ketene 1 1-dimethylpropylcyano-, 55, 38 7-KETOESTERS, 58, 79, 81, 82 7-KETOESTERS TO PREPARE CYCLIC DIKETONES, 58, 83 KETONE terf-butyl phenyl, 55, 122 Ketone, methyl ethyl- 55, 25 Ketone, methyl vinyl, 56, 36 KETONES, acetylenic, 55, 52 Ketones, alkylation of, 56, 52 KETONFS aromatic, aromatic hydrocarbons from 55, 7... 

REACTIONS OF ISATINS WITH CYCLIC KETONES AND DIKETONES... 

A more important example is the synthesis of the rat poison PivaT. An enolizable ketone that is blocked on one side by a tertiary butyl group reacts with diethyl phthalate to give a five-membered cyclic diketone in one reaction by two Claisen ester condensations. 

Until recently, the preparation of the bicyclic ene-diones (47a,b), which are important intermediates in steroid total synthesis, has led only to racemic mixtures This deficiency has now been met as follows. Michael addition of the vinyl ketone (44) to the cyclic diketones (45a) and (45b) afforded the triketo-intermediates (46a) and (46b) in high yield, each containing a prochiral centre. Optically active amines and amino-acids were used as chiral reagents to... 

This reaction has been used for the synthesis of a large variety of aldehydes and ketones - including (i) deuterio aldehydes (ii) optically active aldehydes and ketones (iii) alicyclic (Scheme 60, entry d) and cyclic diketones (Scheme 60, entry including those derived from... 

With a cyclic diketone, triazole formation occurs with simultaneous ring opening of the cyclic ketone moiety (Scheme 14) (78JHC161). 

Active methylene compounds such as 1,3-diketones, 1,3-keto carboxylic esters, malononitrile, and ethyl cyanoacetate were alkylated by alkyl halides catalyzed by the ionic liquid [bmim][OH] under microwave irradiation. The alkyl halides included allyl, benzyl, methyl, and butyl bromides/iodides. The open-chain 1,3-ketones produced the monoalkylated products, whereas the cyclic diketones provided the dial-kylated products in one stroke. Malononitrile and ethyl cyanoacetate also furnished the dialkylated products (Fig. 12.24) [17]. 

Bicyclic and cyclic ketones are also useful intermediates and a series of preparations are given in BICYCLIC KETONES FOR TROPINONE SYNTHESIS 2a,4a-DIMETHYL-8-OXABI-CYCLO[3.2.1]OCT -6-EN-3-ONE CYCLOPENTENONES FROM a,a -DIBROMOKETONES AND ENAMINES 2,5-DI-METHYL-3-PHENYL-2-CYCLOPENTEN-1-ONE y-KETO-ESTER TO PREPARE CYCLIC DIKETONES 2-METHYL-1,3-CYCLOPENTANEDIONE, with the companion preparation y-KETOESTERS FROM ALDEHYDES VIA DIETHYL ARYLSUCCINATES 4-OXOHEXANOIC ACID ETHYL ESTER, which gives the procedure used to prepare the needed... 

Leonard and co-workers12 have studied the spectra of some diaryl ketones and of a series of cyclic diketones... 

Ogata and Yamashita have studied the kinetics of the reaction of phosphites with aliphatic a-diketones and with benzils to give the adducts (48). In all cases the reaction was second-order, first-order in phosphite and ketone. For symmetrical diketones steric effects appear to control the rate, while in unsymmetrical examples electronic effects are much more important. In cyclic diketones the rate constant decreases... 

The reaction of isatoic anhydrides with cyclic ketones and diketones leads to condensed tri- and tetracyclic compounds. For example, the reaction of the anhydrides 2 or 42 with cyclohexen-2-one in the presence of lithium diisopropylamide gave 28-49% yields of the acridine derivatives 43 [25],... 

The intramolecular aldehyde-ketone benzoin reaction catalysed by pre-NHC FI was reported by Suzuki et al. It was found that the size of the substituent at the ketone moiety could influence the enantiomeric excess (Scheme 20.5). Recently, Sakai and Ema reported the intramolecular crossed benzoin reactions of cyclic diketones (Scheme 20.6). " In the presence of 30 mol% of... 

Macrocycle Synthesis Cyclic Ketones, Ketoalkenes, Diketones and Dienes of Ring Size C21 to C26." Foibes. M.D.E. Dang, Y. Org. Prep. Proceed. Ira., 1993, 25, 309... 

New acyl anion equivalents have proved to be popular targets for research and this year is no exception. For example anion (37) reacts with aldehydes (R CHO) to give acrylates (38), and amidrazones (39) provide access to the acyl anion equivalents (40). The latter undergo electrophilic attack to yield ketones [RCH2C(0)E] after unmasking. Similarly, 1,4-diketones are obtained from the addition products of acyl anion equivalent (41) and a,/3-unsaturated ketones. Cyclic a,/3-unsaturated ketones (42) are in turn formed by addition of the /S-acyl anion equivalent (43) to electrophiles. The 5-oxocyclopentenyl equivalent (44, X = Li) is generated in three steps from the cyclopentenone... 

Transannular aldolization is a powerful method for creating two new rings with at least two new stereogenic centers. Chandler and List reported on an enantioselective version of transannular aldolization of cyclic diketone catalyzed by proline derivative 87. 1,4-Cyclooctadione 86 was subjected to the intramolecular aldol reaction in the presence of /ra 5-4-fluoroproline 87 to give the transannular aldol product, (3-hydoxy ketone 88, in 84% yield with 96% ee (Scheme 27.15). In this reaction, proline catalyst bearing a substituent at the 4-position was effective for increasing enantioselectivity. The polycyclic product of 88 was further elaborated into (-l-)-hirustene 89, which is a... 

The rt,/3-unsaturated linear carbonyl compound 39 is obtained by the decomposition of the cyclic hydroperoxide 38 with PdCl2,[35]. The a, 0-epoxy ketone 40 is isomerized to the /3-diketone 41 with Pd(0) catalyst[36]. The 1,4-epiperoxide 42 is converted into the /3-hydroxy ketone 43 and other products[37]. 

Intramolecular acylation of ketones yields cyclic p diketones when the ring that is formed is five or six membered... 

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