Benzaldehyde, olefination

Scheme 17 Benzaldehyde olefination with ethyl diazoacetate/triphenylphosphine/MCM-supported trioxorhenium(Vll) catalyst...

Liquids.—It may be a hydrocarbon (paraffin,olefine,aromatic) Jiiyher alcohol e.g. amyl alcohol), aldehyde [eg., benzaldehyde) ketone [eg., acetophenone) acid [e.g., valeric acid), ether, cdei, phenol [e.g., zveewtiCxaX) phenol ether [e.g, anisole). 

In 1909, Patemo and Chieffi noted that mixtures of tri- or tetra-substituted olefins and aldehydes formed trimethylene oxides when exposed to sunlight. Biichi later repeated Patemo s experiments by irradiating 2-methyI-2-butene in the presence of benzaldehyde, butyraldehyde, or aeetophenone and rigorously purifying and identifying the resulting products. The reaction thus bears the name of its two primary pioneers and has come to represent any photo-catalyzed [2 + 2] electrocyclization of a carbonyl and an alkene. 

Evans Jr. and coworkers reported a similar olefination reaction employing spirooxyphosphoranes of type 66. Upon treatment with a strong base (LiHMDS) and subsequent addition of benzaldehyde, the reaction proceeded to form anionic P(VI) intermediates (67,6 -106 to -116 ppm) that decomposed at room temperature to form the corresponding olefins and spiropentaoxyphosphoranes [ 105]. The stereoselectivity (E Z ratio) of the double bond-forming reaction depended upon the conditions evidence indicated the possibility of kinetic or thermodynamic control (Scheme 21). 

The formation of ethers such as 1806 by EtsSiH 84b can also be catalyzed by trityl perchlorate to convert, e.g., benzaldehyde in 84% yield into dibenzyl ether 1817 [48]. The combination of methyl phenethyl ketone 1813 with O-silylated 3-phenyl-n-pro-panol 1818, in the presence of trityl perchlorate, leads to the mixed ether 1819 in 68% yield [48] (Scheme 12.15). Instead of trityl perchlorate, the combination of trityl chloride with MesSiH 84a or EtsSiH 84b and sodium tetrakis[3,5-bis-(trifluoro-methyl)phenyl]borane as catalyst reduces carbonyl groups to ethers or olefins [49]. Employing TMSOTf 20 as catalyst gives very high yields of ethers. Thus benzaldehyde reacts with O-silylated allyl alcohol or O-silylated cyclohexanol to give the... 

A polymer containing side-chain benzylphosphonium residues has been prepared and used in olefin synthesis. A suspension in THF was treated with base and benzaldehyde overnight and the polymeric phosphine oxide was then removed by filtration. The yields of stilbenes, 40% with potassium t-butoxide and 60% with sodium hydride, were not improved by using an excess of base or of aldehyde. 

Corey and Chaykovsky found that the dimsyl anion reacts with benzophenone and benzaldehyde to afford the corresponding 9-hydroxysulfoxides 109 and 110. Thermal decomposition of these jS-hydroxysulfoxides was shown to give a, -unsaturated sulfoxides or olefins . Thus, the reaction of dimsyl anion with benzophenone at 100 °C gave 1,1-diphenylethylene, diphenylmethane, 1,1-diphenylcyclopropane and diphenylacetaldehyde, besides 1, l-diphenyl-2-methylthioethylene . 

The synthetic method leading to Nb-alkylidenes and Nb-alkylidynes was particularly successful, due to a quite remarkable difference in the reaction rate of 29 with ketones or aldehydes, vs the subsequent reaction of the alkylidene with ketones and aldehydes (see Scheme 37). The former reaction takes a few minutes at -40°C, while the latter one occurs in hours at room temperature.88 The reaction between 178 and benzaldehyde led to triphenylethylene and the niobyl derivative 184. Due to the difference in reaction rates between a and b in Scheme 37, it was found that the sequential addition of two different ketones or aldehydes to a THF solution of 29 produced a nonsymmetric olefin in a stepwise McMurry-type reaction.84 This is exemplified in the coupling shown in reaction c (Scheme 37). The proposed reaction pathway does not involve the intermediacy of a pinacolato ligand and therefore differs from the mechanism of the McMurry reaction and related reductive couplings at activated metal sites.89... 

Aldehydes do not co-oxidize alkanes due to a huge difference in the reactivity of these two classes of organic compounds. Alkanes are almost inert to oxidation at room temperature and can be treated as inert solvents toward oxidized aldehydes [35]. Olefins and alkylaromatic hydrocarbons are co-oxidized with aldehydes. The addition of alkylaromatic hydrocarbon (R2H) to benzaldehyde (R1H) retards the rate of the initiated oxidation [36-39]. The rate of co-oxidation obeys the equation [37] ... 

Mukai et al.85 reported an asymmetric 1,3-dipolar cycloaddition of chromium(0)-complexed benzaldehyde derivatives. As shown in Scheme 5 52, heating chiral nitrone 171a, derived from Cr(CO)3-complexed benzaldehyde, with electron-rich olefins such as styrene (173a) or ethyl vinyl ether (173b) generates the corresponding chiral a.v-3,5-disubstitutcd isoxazolidine adduct 174 or... 

As in the case of other groups which activate adjacent CH6, the nitro group in aliphatic nitro compounds soon acquired importance in preparative organic chemistry, particularly for condensation reactions. The condensing agents are normally bases. Thus nitromethane will react with benzaldehyde to give first a nitro-alcohol and then a nitro-olefin (Priebs, 188425) ... 

After these results had established the feasibility of generating and utilizing a carbohydrate phosphorane, the two systems that had been reported earlier were examined in order to determine if similar conditions would allow them to undergo the Wittig reaction. The ylide derived from phosphonium salt I condensed with both benz-aldehyde and U-chlorobenzaldehyde to produce good yields of olefinic products Villa and Vlllb. The ylide derived from phosphonium salt II also was successfully condensed with benzaldehyde, but the yield of IX was only 30 , presumably because of its extremely poor solubility even in an HMPA-THF solvent mixture. Both of these systems supported the tenet that it was possible to use unstabilized carbohydrate phosphoranes if the conditions are proper and if the g-oxygen is attached to the carbohydrate through another set of bonds. 

As described above in Eq. 43, simple allylboronates can be transformed into more elaborated ones using olefin cross-metathesis. " Treatment of pinacol allylboronate 31 with a variety of olefin partners in the presence of Grubbs second-generation catalyst 142 smoothly leads to formation of 3-substituted allylboronates 143 as cross-metathesis products (Eq. 104). Unfortunately, these new allylic boronates are formed as mixtures of geometrical isomers with modest E/Z selectivity. They are not isolated but rather are treated directly with benzaldehyde to give the corresponding homoallylic alcohol products in good yields (Table A). 

Table A. Functionalized homoallylic alcohols from olefin cross metathesis and subsequent allylboration reactions with benzaldehyde...

The (Z)- and ( )-styrylpyrazine structures 20j and 20k were assigned on the base of the mass, NMR, and UV spectral data. The mass spectrum of Z isomer (20j) shows a base peak (the molecular ion) at m/z 210 with a peak at m/z 133 formed by the loss of a phenyl group firom 20j. The H-NMR spectrum shows the presence of five aromatic and two olefinic protons in addition to one heteroaromatic proton and two methyl groups attached to the heteroaromatic nucleus. Ozonolysis of the Z isomer (20j) yields 3-formyl-2,5-dimethylpyrazine (487) and benzaldehyde, confirming the styryl moiety in 20j. The ( )-styryl derivative (20k) is readily isomerized to the Z isomer (20j) on exposure to sunlight (Scheme 60). Extraction of the pyrazines from I. humillis in the dark indicates that E isomer 20k is the naturally occurring product 144,145). 

The product hydrazide may be sulfonated and decomposed by heating with a base in ethylene glycol to yield benzaldehyde, CeHsCHO. Many aromatic aldehydes may be produced by similar routes. The hydrazone derivative of toluenesulfonic acid reacts with an aldehyde or a ketone in the presence of a base catalyst, such as sodium ethoxide, to yield the corresponding olefin (Bamford-Stevens reaction) ... 

Solid styrene was exposed at — 196°C to ozone, in an attempt to discern whether the behavior of the system is similar to that of olefinic compounds, yielding an ozonide, or to that of aromatic compounds, yielding a 7r-complex. On heating to about — 100°C, an adduct is formed that is stable until about —55 °C, when benzaldehyde and a peroxidic polymer are slowly obtained. The structure of the adduct is probably that of a POZ, based on the similarity of the IR spectrum with the ozone adduct of vinyl chloride described in the preceding paragraph . 

In related studies, it has been shown that a-fluorobenzylphosphonates ArCHFPO(OEt)2 (38) will undergo Wadsworth-Emmons-type olefination reactions with aldehydes and ketones [57]. 39 was prepared from benzaldehydes and HP(0) (OEt)2, which was fluorinated using diethylaminosulfur tiifluoride for example, diethyl [(3,5-dimethylphenyl)(fluoro)methyl]phosphonate (38) was formed in 91%. An 82% yield of Me 2-[(fluoro)(4-fluorophenyl)methylene]butanoate (1 1 E Z) (40) was obtained from 38 and methyl 2-oxobutanoate (Scheme 13). 

The first attempt to prepare 2-phenyl-4-(phosphoranylidene)-5(4//)-oxazolone 219 started with l-benzoylamino-(2,2-dichloroethenyl)triphenylphosphonium chloride 216 and involved the complex reaction sequence shown in Scheme 7.67. The structure and properties of 219 were studied and it was shown that 219 underwent Wittig olefination with benzaldehyde to give the well-known (Z)-4-benzylidene-2-phenyl-5(477)-oxazolone. ... 

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