Acrylic derivatives, 117 Aldehydes

The asymmetric Baylis-Hillman reaction of sugar-derived aldehydes as chiral electrophiles with an activated olefin in dioxane water (1 1) proceeded with 36-86% de and in good yields of the corresponding glycosides (Eq. 10.47).104 The use of chiral /V-mcthylprolinol as a chiral base catalyst for the Baylis-Hillman reaction of aromatic aldehydes with ethyl acrylate or methyl vinyl ketone gave the adducts in good yields with moderate-to-good enantioselectivities in l,4-dioxane water (1 1, vol/vol) under ambient conditions.105... 

The ease of racemization of chiral a-amino aldehydes under MBH conditions is undoubtedly a major difficulty in studying diastereoselective reactions [53]. Epi-merization can be essentially avoided by conducting the reaction at low temperature [54, 67], or it can be minimized at room temperature when a conformation-ally restricted amino aldehyde, such or N-trityl-azetidine 2-(S)-carboxyaldehyde is used [54]. The use of ultrasound also increases the rate of the MBH reaction, avoiding racemization almost completely, even at room temperature [55]. When adding various a-amino acid-derived aldehydes to methyl acrylate using DABCO... 

N,N DIPROP YL-4-TRIFLUORO-METHYL-2,6-DINITROANILINE (1582-09-8) Ci3HjsF3N304 Combustible solid (flash point >185 F/>85°C oc Fire rating 1). May react violently with barium, potassium, sodium. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Exothermic decomposition with maleic anhydride. May increase the explosive sensitivity of nitromethane. Reacts with nitroalkanes, forming explosive products. As a dinitroaniline derivative, the extremes of heat (do not store above 90°F/32°C), mechanical shock, and fnction might be... 

Application of RCM to acrylates derived from terpene aldehydes containing a remote double bond yielded the 6-substituted dihydropyran-2-ones <01TL6069> and oxabicyclo-[3.2.1]octane undergoes an efficient ring-opening cross-metathesis with electron-rich alkenes to give unsymmetrically 2,6-disubstituted tetrahydropyran-4-ones <01OL4275>. 

The MBH adducts, derived from methyl acrylate and aldehydes, have been employed successfully to the general synthesis of 3-arylidene(alkylidene)chro-man-4-ones 94, which involved an intramolecular Friedel-Crafts reaction as... 

A ligand-independent, osmium-catalyzed aminohydroxylation of MBH adduct has been developed by Sharpless et al. (Scheme 3.202). The yield, rate and selectivity of this reaction are not affected by the addition of cinchona alkaloid ligands. The diastereoselectivity for the aminohydroxylation is influenced by the aldehyde-derived substituent, while the acrylate-derived substituent has a minimal effect. Various derivatives and close analogs of the MBH product-core failed to aminohydroxylate, emphasizing the unique reactivity of this class of olefins. 

MBH adducts and their derivatives derived from methyl acrylate and aldehydes undergo stereoselective cycloadditions with diazomethane and benzonitrile oxide to give the corresponding cycloadducts in good yields (Scheme 3.214). The stereochemical outcome can be explained by the so-called inside alkoxy elfect theory.However, in the case of diazomethane cycloadditions, electrostatic factors play a reduced role compared to the corresponding nitrile oxide reactions, while steric elfects are of major importance in governing the stereoselectivity. This dilferent behavior of the two 1,3-dipoles has been rationalized by analysis of the atomic charges, as calculated at the RHF/3-21G level of theory, for the transition structure of these reactions. 

Alcaide and Almendros have developed a novel palladium-catalyzed domino heterocyclization/cross-coupling reaction of various a-allenols and MBH acetates, furnishing [(2,5-dihydrofuran-3-yl)methyl]acrylate derivatives 489 and 490 and the acrylonitrile 491 in moderate to good yields (Scheme 3.216). " Ozonolysis of MBH adducts originating from aromatic aldehydes provides a-ketoesters 492 with different substitution patterns on the aromatic ring. Diastereoselective reduction of the a-ketoesters 492 affords the corresponding a,p-dihydroxy-esters 493 with excellent anti diastereoselectivity. This method provides an alternative approach for the synthesis of either a-ketoesters or a,p-dihydroxy esters (Scheme 3.217). ... 

Chiral phosphines, which arc widely used in enantioselective synthesis, have been also explored in the MBH-reaction (Fig. 4.49). Thus, (5)-BINAP 252 (20 mol%) have been used as catalyst in the reaction of several alkyl acrylates 237 (R =alkox-ides) with pyrimidine derived aldehydes in chloroform at 20°C, providing the expected products in low yields (8-26%) and moderate enantioselectivities (9-44% ee) [326]. Although better yield (83%) was encountered by using phospholane 253 (10 mol%) using methyl acrylate as starting material and solvent at 25 C, product 241 was obtained in only 17% ee [327]. 

The Baylis-Hillman alkenes (106) undergo a facile osmium-catalysed aminohy-droxylation reaction (Scheme 12), whose diastereoselectivity is influenced mainly by the aldehyde-derived substituent the acrylate-derived substituent has a minimal effect (Table 1). ... 

Apart from the thoroughly studied aqueous Diels-Alder reaction, a limited number of other transformations have been reported to benefit considerably from the use of water. These include the aldol condensation , the benzoin condensation , the Baylis-Hillman reaction (tertiary-amine catalysed coupling of aldehydes with acrylic acid derivatives) and pericyclic reactions like the 1,3-dipolar cycloaddition and the Qaisen rearrangement (see below). These reactions have one thing in common a negative volume of activation. This observation has tempted many authors to propose hydrophobic effects as primary cause of ftie observed rate enhancements. 

The versatility of this reaction is extended to a variety of aldehydes. The bisphenol derived from 2,6-di-/ f2 -butylphenol and furfural, (25) where R = furfuryl (13), is also used as an antioxidant. The utility of the 3,5-di-/ f2 -butyl-4-hydroxyben2yl moiety is evident in stabili2ets of all types (14), and its effectiveness has spurred investigations of derivatives of hindered alkylphenols to achieve better stahi1i2ing quaUties. Another example is the Michael addition of 2,6-di-/ f2 -butyl phenol to methyl acrylate. This reaction is carried out under basic conditions and yields methyl... 

Carbon, hydrogen and possibly oxygen Resin and derivatives Natural drying oils Cellulose derivatives Alkyd resins Epoxy resins (uncured) Phenol-formaldehyde resins Polystyrene Acrylic resins Natural and synthetic rubbers Carbon monoxide Aldehydes (particularly formaldehyde, acrolein and unsaturated aldehydes) Carboxylic acids Phenols Unsaturated hydrocarbons Monomers, e.g. from polystyrene and acrylic resins... 

In the case of enamines derived from aldehydes a cycloaddition to give a cyclobutane occurs (48-50). Thus the enamine (16) reacted with methyl acrylate in acetonitrile to give a 91 % yield of methyl 2-dimethylamino-3,3-dimethylcyclobutane carboxylate (56). Similarly, treatment of (16) with diethylmaleate at 170° gave a 70% yield of diethyl 4-dimethylamino-3,3-dimethyl-l,2-cyclobutanedicarboxylate (57), and 16 and acrylonitrile gave a 65% yield of 2-dimethylamino-3,3-dimethylcyclobutanecarbonitrile (58). 

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