Formaldehyde Prins condensation

With Ga-Beta it was found that, when the Si/Ga ratio increased from 10 to 40, the number of strong sites decreased drastically for Si/Ga between 10 and 25 and then reached a plateau above Si/Ga = 25 [53], The strength and density of acid sites in H(Ga, La)-Y were also found to be lower than those in HY crystals of the type used in FCC preparation (LZY-82) [250], Similar catalytic selectivities were obtained for both Ga-ZSM5 and A1-ZSM5 in Prins condensation of isobutylene with formaldehyde. Catalytic tests coupled with microcalorimetric measurements have shown that medium to weak acid strength sites favor the selectivity to isoprene [254],... 

Dioxanes can also be produced by the acid-catalysed condensation of alkenes with aldehydes, preferably with formaldehydes Prins reaction) ... 

Scheme 5.6-2 Prins condensation of isobutene with formaldehyde (MBD 3-methylbutane-l,3-diol, DMD 4,4-dimethyl-l,3-diol, MBOH 3-methyl-3-buten-l-ol catalyzed by tin (IV) chloride species [75].

Catalytic tests of Prins condensation of isobutylene with formaldehyde over iron-substituted MFI catalysts have shown that medium to weak acid strength sites favor the selectivity to isoprene [241]. [Ga]-ZSM5 was also tested as a catalyst for this condensation, but its catalytic selectivity was rather close to that of [A1]-ZSM5 [241]. 

H.J. Prins, Condensation of formaldehyde with some unsaturated compounds, Chem. Weekbl 16 (1919) 1072-1073. 

E. Dumitriu, V. Hulea, I. Fechete, C. Catrinescu, A. Auroux, J.F. Lacaze, C. Guimon et al., Prins condensation of isobutylene and formaldehyde over Fe-sUicates of MFI structure. Appl. Catal. A Gen. 181, 15-28 (1999)... 

PdCb-CuCb catalyzes the condensation of branched-chain alkenes with formaldehyde to give the l,3-dioxanes 96a and 96b (Prins reaction)[73]. The yields are much higher than in the conventional acid-catalyzed Prins reaction. 

An important synthetic process for forming a new carbon—carbon bond is the acid-catalyzed condensation of formaldehyde with olefins (Prins reaction) ... 

Condensation of vinyl chloride with formaldehyde and HCl (Prins reaction) yields 3,3-dichloro-l-propanol [83682-72-8] and 2,3-dichloro-l-propanol [616-23-9]. The 1,1-addition of chloroform [67-66-3] as well as the addition of other polyhalogen compounds to vinyl chloride are cataly2ed by transition-metal complexes (58). In the presence of iron pentacarbonyl [13463-40-6] both bromoform [75-25-2] CHBr, and iodoform [75-47-8] CHl, add to vinyl chloride (59,60). Other useful products of vinyl chloride addition reactions include 2,2-di luoro-4-chloro-l,3-dioxolane [162970-83-4] (61), 2-chloro-l-propanol [78-89-7] (62), 2-chloropropionaldehyde [683-50-1] (63), 4-nitrophenyl-p,p-dichloroethyl ketone [31689-13-1] (64), and p,p-dichloroethyl phenyl sulfone [3123-10-2] (65). 

In the Cannizzaro reaction (62), which involves self-condensation of aldehydes that have no a-hydrogen atoms, the nucleophile is represented best as a hydride ion in the Prins reaction (26), the nucleophile is an olefin in the aldol condensation (63) and reaction of methyl acetate with formaldehyde (62), the nucleophile is a methylene group a- to a... 

The continuous increase of isoprene demand has determined the enhancement of researches focused on the elaboraticxi of new and efficient routes for the industrial synthesis of this valuable diene. The acid-catalyzed cc ensation of formaldehyde and isobutene, known as Prins reacticxi, is already a recognized industrial route for the isoprene synthesis, being applied as two-stages process, condensation to form 4,4-dimethyl-l,3-dioxane in the presence of an aqueous sulphuric acid and its decomposition to isoprene using solid phosphoric acid catalysts. 

This reaction was first reported by Kriewitz in 1899. It is the condensation between formaldehyde and olefins to form unsaturated primary alcohols under conditions of high temperature (e.g., 170°C). In this reaction, water or acetic acid is usually applied as the solvent, and an acid is added as a catalyst, such as sulfuric acid. Under these conditions, formaldehyde and some ketones function as an enophile. The double bond in the new unsaturated alcohol is adjacent to its original position in the starting olefin," with the exception of camphene, which gives an allylic alcohol. For the acylic olefins in this condensation, the isobutylene-type olefins are much more reactive than the monosubstituted olefins or 1,2-disubstituted olefins. The further extension of this reaction involving an intramolecular condensation of an a-alkoxycarbenium ion with a double bond to form a hydropyran derivative is known as the Prins-Kriewitz cyclization. ... 

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