Reaction with aryl aldehydes

C-7 methyl substituents on the 7-methylpyrazino[2,3-( ][l,2,6]thiadiazine 88 undergo aldol condensation reactions with aryl aldehydes to give the 7-styryl compounds 89 as shown in Scheme 12. It is interesting to note that the 6-methyl analogues 90 do not react, a consequence of the lower acidity of the 6-methyl group <2003HCA139>. 

Scheme 3 Silyl diene as substrate in Ni-catalyzed coupling reactions with aryl aldehydes...

Sulfur ylides, derived from benzyl bromides and an optically active alkyl sulfide, undergo base-promoted reactions with aryl aldehydes to produce optically active 1,2-diatyl epoxides.The reaction is illustrated by equation (17) and produces epoxides with optical purities in the range of 28-47% ee. The bicyclic sulfide shown in equation (17) was derived from (-t-)-camphor8ulfonic acid and produces the (RiO-enantiomer of the epoxide in excess. 

Indolylmethylphosphonates (370) have been prepared from the corresponding bromides and undergo Wittig reactions with aryl aldehydes to yield styryl compounds (371) the 3-phenylthio group can be removed by reduction (Scheme 125) <85S188>. 

In the ruthenium-catalyzed tandem olefin migration of 3-buten-2-ol and aldol reaction with aryl aldehydes, catalytic In(OAc)3 was found to be essential to elevate the poor yields to moderate and good levels [278] (Figure 8.125). Similar results were observed for the same reaction in ionic liquids [279]. 

When allylic alcohols are used as an alkene component in the reaction with aryl halides, elimination of /3-hydrogen takes place from the oxygen-bearing carbon, and aldehydes or ketones are obtained, rather than y-arylated allylic alcohoIs[87,88]. The reaction of allyl alcohol with bromobenzene affords dihydrocinnamaldehyde. The reaction of methallyl alcohol (96) with aryl halides is a good synthetic method for dihydro-2-methylcinnamaldehyde (97). 

Homoenolate Reactivity The ability to generate homoenolates from enals and its application to the preparation of y-butyrolactones 30, through reaction with an aldehyde or aryl trifluoromethyl ketone, was reported independently by Glorius [8], and Bode and Burstein [9] (Scheme 12.4). A sterically demanding NHC catalyst is required to promote reactivity at the d terminus and to prevent competitive benzoin dimerisation. Nair and co-workers have reported a similar spiro-y-lactone formation reaction using cyclic 1,2-diones, including cyclohexane-1,2-dione and substituted isatin derivatives [10]. 

Fe. Iron metal was found to be able to mediate the allylation reactions of aryl aldehydes with allyl bromide using sodium fluoride as the promoter. The formation of an allyliron species was proposed as the reactive intermediate in the reaction (Scheme 8.20).187 In view of... 

Classical Aldol. Aldol reaction is an important reaction for creating carbon-carbon bonds. The condensation reactions of active methylene compounds such as acetophenone or cyclohexanone with aryl aldehydes under basic or acidic conditions gave good yields of aldols along with the dehydration compounds in water.237 The presence of surfactants led mainly to the dehydration reactions. The most common solvents for aldol reactions are ethanol, aqueous ethanol, and water.238 The two-phase system, aqueous sodium hydroxide-ether, has been found to be excellent for the condensation reactions of reactive aliphatic aldehydes.239... 

A modified Pictet-Spengler reaction has been applied to the synthesis of thiazolo-quinolines 58 <06T3228>. Condensation of anilines 53 with aryl aldehydes 54 followed by endo cyclization results in the formation of thiazoloquinolines 58 under a variety of traditional Pictet-Spengler protocols such as 2% trifluoroacetic acid in dichloromethane. 

The reaction of 2,3-diaminoquinazolin-4-one 404 with aryl aldehydes and thioglycolic acid gives 2-substituted 1,3-dihydro-thiazolo[3, 4 2,3][l,2,4]triazolo[5,l-A]quinazolin-5-ones 405 (Equation 79) <2004MI10>. 

The catalysed alkylation of l//,4//-pyrazol-5-ones is solvent dependent. In benzene, bis-alkylation occurs at the 4-position whereas, in a carbon disulphide benzene mixture, O-alkylation is observed, although the major product (4, Scheme 5.22) results from nucleophilic attack by the pyrazolone on the carbon disulphide, followed by alkylation of the dithiolate dianion [92]. The catalysed reaction of 2-thiono-3-aryl-thiazolidin-4-ones with alkylating agents under soliddiquid two-phase conditions results in alkylation at the 5-position (60-80%) [93]. The aldol condensation of the thiazolidinones with aryl aldehydes is also catalysed by quaternary ammonium salts. 

Under basic liquiddiquid two-phase conditions the reaction of aryl aldehydes with benzyldibutyltelluronium bromide produces oxiranes [71] although, in some instances, alkenes are formed. 

The catalysed reaction of aryl aldehydes with ammonia and chloroform (7.4.3) in the presence of chiral ephedrinium salts leads to the asymmetrically induced formation of a-amino acids. Yields are variable and with ca. 20-30% ee [49]. 

Reaction between C2 symmetric diols and a, yS-unsaturated aldehydes yield chiral ethylenic acetals that undergo copper-mediated substitution reactions. With aryl or... 

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