Protons formaldehyde complexes

In 1979 the results of ab initio calculations at the 4-3IG and 6-3IG level on the same complex as well as a formaldehyde/H+ complex were reported. Structural and energetic ctxnparisons of the two complexes showed that while Li+ prefers a linear geometry for electrostatic ion-dipole bonding, the proton coordinates to the carbonyl through a largely covalent bond, resulting in a bent structure (Cs symmetry)... 

When DMSO is mixed with concentrated hydrochloric acid, protonated DMSO is in equiUbtium with the chlorodimethylsiilfonium ion. Pummerer reactions and subsequent reaction of the initial products give a complex mixture of products including formaldehyde, bis(methylthio)methane, methanethiol, dimethyl disulfide, dimethyl sulfide, and others. 

A rather more complex amino alcohol side chain is accessible by a variation of the Mannich reaction. Taking advantage of the acidic proton in acetylenes, propargyl acetate (62) is condensed with formaldehyde and dimethylamine to give the acetylated amino... 

Pd, or Ni (Scheme 5-3). First, P-H oxidative addition of PH3 or hydroxymethyl-substituted derivatives gives a phosphido hydride complex. P-C bond formation was then suggested to occur in two possible pathways. In one, formaldehyde insertion into the M-H bond gives a hydroxymethyl complex, which undergoes P-C reductive elimination to give the product. Alternatively, nucleophilic attack of the phosphido group on formaldehyde gives a zwitterionic species, followed by proton transfer to form the O-H bond [7]. 

Formyl complexes show varying behavior when treated with protonating agents. Reaction of (CO)4Fe(CHO)" (22) with acid gives formaldehyde in 13-20% yield (27-29). Homologous (CO)4Fe(COR) acyls afford excellent yields of aldehydes when protonated, presumably via... 

The first step is a carbonyl ene reaction, also known in the literature as a Prins reaction.7 A Lewis acid activates formaldehyde (25) for attack on the double bond of 12. This results in zwitterionic intermediate 26, which leads to the ene product 27 in the form of a dimethylaluminum complex through 1,5-migration of a proton. This complex is unstable and spontaneously eliminates methane. Aqueous workup hydrolyzes aluminum alkoxide 28 to alcohol 24. 

When there is a substituent on the benzene ring, a benzylic methylene proton at the meta position is more activated than the para position. Reaction of formaldehyde on the complexed estradiol derivative 246 occurred regioselectively and stereoselectively from the opposite side of Cr(CO)3 to give 247 [62],... 

Calixarenes are formed by condensation of a p-substituted phenol with formaldehyde [8]. These macrocycles are conformationally quite flexible but, by introducing suitable substituents in the aromatic subunits, the so-called cone conformation, in which all aromatic subunits point into the same direction, can be stabilized. This conformation is usually best suited to complex guest molecules because it has a well defined hydrophobic cavity. An inclusion of cations such as ammonium ions or quaternary ammonium ions into this cavity can be demonstrated, for example, by the characteristic upfield shifts of guest signals in the NMR, an effect that is a consequence of the close proximity of the corresponding protons to the surfaces of the aromatic receptor subunits in the complex. 

Formed holes oxidize water giving molecular oxygen and protons. The Rum complex is reduced to the Ru11 one, which reacts with C02. Formic acid and formaldehyde are formed as a result of the reduction process. 

They also applied this method to the intermolecular ene reactions of aliphatic and aromatic aldehydes with alkenes containing a disubstituted vinylic carbon, a potentially valuable route to homoallylic alcohols [50]. Proton-initiated rearrangements do not take place, because the alcohol-Lewis acid complex formed in the ene reaction reacts readily to give methane and a non-acidic aluminum alkoxide. Formaldehyde and excess Me2AlCl gave good yield of ene adducts with all types of alkene, as exemplified in Sch. 26. 

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