Esters, conjugated, preparation from

Asymmetric conjugate addition of RiCuLij The chiral crotonyl ester 1, prepared from (+ )-camphor by addition of 1-naphthylmagnesium bromide followed by esterification with crotonic acid, undergoes conjugate addition with BuaCuLi at -25° to give the adduct 2 in 95% de. Reduction of 2 with LiAUtj gives (S)-3-... 

The importance of the problem may be assessed from the example of conjugated catalytic reactions in which the acrylic, propionic, succinic and maleic acid esters are prepared from CO and C2H2 in alcoholic solutions of Pd I) complexes"". The total number of hypotheses, generated on the simplest possible assumption that the final product is formed in a single sequence of intermediates. is 1344 ... 

Acridinium Conjugate Prepared from a Mab anti-human IgG conjugated with 10-(3-sulfopropyl)-N-tosyl-N-(2-carboxyethyl)-9-acridinium carboxamide via N-hydroxysuccinimide ester in a phosphate buffer. After conjugation, the conjugate was sized by HPLC to a pool of fractions with Ac/IgG molar ratios ranging from 3 to... 

Highly stabilized phosphorus ylides are prepared from acetylenic esters, a carbon-based nucleophile, and triphenylphosphine in aqueous media.40 In acetone-water (2 1) solvent, the reaction proceeds via the conjugate addition of triphenylphosphine to dialkyl acetylenedicarboxy-lates the resulting vinyl triphenylphosphonium salts undergo Michael addition reaction with a carbon-nucleophile to give the corresponding highly stabilized phosphorus ylides. 

The cross-conjugated trienes have potential in many different types of diversification strategies. For example, the triene clearly lends itself to inter- and intramolecular Diels-Alder reactions. Incorporation of the hydroxymethyl group on the tether allows attachment of functionality suitable for reactions subsequent to the Alder-ene reactions. As depicted in Scheme 8.5, propargyl tosylamides A, alkynyl silanes B, acrylate esters C, and propargyl ethers D can all be readily prepared from 39... 

Absorption and Deposition of CLA in Animal Tissues. Miller etal (27) described a method employing the methyl ester of conjugated dienes prepared from com oil as tracers of fat metabolism. It was postulated that the conjugated dienoic isomers could be differentiated from other fatty acids in body fat by spectrophotometric absorbance at 233 nm. 

Except for the well-documented conjugate additions of diethylaluminum cyanide,92 triethylaluminum-hydrogen cyanide and Lewis acid-tertiary alkyl isonitriles,93 examples of Lewis acid catalyzed conjugate additions of acyl anion equivalents are scant Notable examples are additions of copper aldimines (233),94, 94b prepared from (232), and silyl ketene acetals (234)940 to a,(3-enones which afford 1,4-ketoal-dehydes (235) and 2,5-diketo esters (236), respectively (Scheme 37). The acetal (234) is considered a glyoxylate ester anion equivalent. 

Finally, chiral 2//-azirine-2-carboxylic esters 128 can be prepared from the corresponding aziridines 127 under mild Swem oxidation conditions. This method, which is effective for both cis and trans substrates, introduces the double bond regioselectively at the "non-conjugated" site [95TL4665]. 

Alkyl halides (particularly bromides) undergo oxidative addition with activated copper powder, prepared from Cu(I) salts with lithium naphthalenide, to give alkylcopper species10. The alkyl halides may be functionalized with ester, nitrile and chloro functions ketone and epoxide functions may also be tolerated in some cases11. The resulting alkylcopper species have been shown to react efficiently with acid chlorides, enones (conjugate addition) and (less efficiently) with primary alkyl iodides and allylic and benzylic bromides (equations 5 and 6). If a suitable ring size can be made, intramolecular reactions with epoxides and ketones are realized. 

Alkenylboronic acids and esters underwent conjugated addition to ct,/ -unsaturated ketones in the presence of trifluoroborane etherate589 or cyanuric fluoride (Equation (129)).590,591 Alkadienyl trifluoromethyl ketones were stereoselectively prepared from (2-alkoxyvinyl) trifluoromethyl ketones (Equation (130)).592 Alkynyl boronates can transfer the alkynyl groups regioselectively and enantioselectively to enones (Equation (131 )).593... 

Silylketene acetal (154) was directly prepared from a-silyl ester (153) in xylene at 230 C to give after acid hydrolysis the desired stereoisomer (155) in 72% overall yield with 6 1 stereoselectivity. Silylketene acetals are also obtained by TMS-Cl accelerated conjugate addition of cuprates. The latter method suffers presently from low diastereoselectivities, though it offers the attractive possibility of one-pot formation of two carbon-carbon bonds and three contiguous chiral centers (equation 15). 

The Lewis acid-catalyzed conjugate addition of silyl enol ethers to a,y3-unsaturated carbonyl derivatives, the Mukaiyaraa Michael reaction, is known to be a mild, versatile method for carbon-cabon bond formation. Although the development of catalytic asymmetric variants of this process provides access to optically active 1,5-dicarbonyl synthons, few such applications have yet been reported [108], Mukiyama demonstrated asymmetric catalysis with BINOL-Ti oxide prepared from (/-Pr0)2Ti=0 and BINOL and obtained a 1,4-adduct in high % ee (Sch. 43) [109]. The enantioselectiv-ity was highly dependent on the ester substituent of the silyl enol ether employed. Thus the reaction of cyclopentenone with the sterically hindered silyl enol ether derived from 5-diphenylmethyl ethanethioate proceeds highly enantioselectively. Sco-lastico also reported that reactions promoted by TADDOL-derived titanium complexes gave the syn product exclusively, although with only moderate enantioselectiv-ity (Sch. 44) [110]. 

Various preparations of antisera to atropine have been reported. A racemic hemisuccinate ester was prepared and conjugated to bovine serum albumin by the carbodiimide technique. Antisera formed to the original immunogen selectively bound the R isomer (34), but a later antiserum prepared by this approach was reported to bind both R and S forms with "equal efficiency" (35). R, S-atropine was treated with diazotized p-amino-benzoic acid, and the resulting compound (which was not further characterized) was used for conjugation to bovine serum albumin by means of a carbodiimide-mediated reaction. Antisera resulting from use of this material were quite selective for the R isomer, with a cross-reaction of only about 2% for the S isomer (36). Virtanen et al. followed this procedure with S-atropine. Their antiserum bound equally to S- and R,S-atropine, as measured by displacement of tritium-labeled R,S-atropine (37). In another study (31), both racemic atropine and the S isomer were coupled to human serum albumin by the technique of Wurtzburger et al. (36), Antisera were obtained that were selective for both the R and S isomers (33). 

Cyclopropane derivatives have been prepared from reactions of arsonium ylides with conjugated enones " and a, jS-unsaturated esters "" . Initial Michael-type reaction is followed by intramolecular elimination of triphenylarsine, e.g. equation 22. These reactions often give high yields and show high stereoselectivity. 

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