Hoffmann elimination product

It has already been reported that the weight loss of as-synthesized MMSs depends on the kind of the template used in the synthesis [17]. This is an obvious consequence of the fact that different templates decompose and thermodesorb at different temperatures. However, it was somewhat unexpected that the decomposition/desorption of the same kind of the template may be dramatically influenced by the framework composition of materials [4,10-14]. This can be understood as an influence of the framework structure on the process of Hoffmann elimination of alkylammonium to the corresponding alkene and low molecular weight amine [4,8], This decomposition process leads not only to the elimination of the electrostatic framework-template interactions but also to the formation of decomposition products of lower molecular weight than that of the surfactant. Thus, the framework-surfactant interactions are crucial factors determining the thermogravimetric behavior. 

Vinyl substitutions on alkenes not having their double bonds conjugated with carbonyl groups often proceed more rapidly and give better product yields when the reactions are conducted in the presence of an unhindered secondary amine. Conjugated and nonconjugated dienes are usually only minor products in these cases. The major products normally are allylic amines obtained by nucleophilic attack of the secondary amine upon the ir-allylpalladium intermediates. Since allylic amines may be quatemized and subjected to the Hoffmann elimination, this is a two-step alternative to the direct vinyl substitution reaction.90... 

When LDA was used in place of butyllithium, l,l-bis(trimethylsilyl)ethylene (Hoffmann-type elimination product) was obtained as the main product (71 %).214... 

Reaction with a-silyltertiary aliphatic amines leads to results of the same type, including silyl- and non-sily 1-products, proceeding either from a Stevens rearrangement or a Hoffmann elimination.364... 

Another example is the reaction of benzyne with 1-methyl- (and benzyl)-3, 3-dimethylbenzo[d]-l,3-azasiloline (see their preparation in Section IV.A.2.p). Stevens rearrangement product is obtained (48%) as a single compound. If a Me on nitrogen is replaced by an Et, then Hoffmann elimination occurs.251 It should be noted that an Y-alkyl MSMA is converted into an Y-aryl RSMA in the former case and into a Y-aryl MSMA in the latter case. 

The product, which contains both the double bond and the tertiary amine in an ring-opened structure, can undergo a second Hoffmann elimination. 

The use of optically active enamines in [2 + 2] cycloadditions with thiocarbonyl 5.5-dioxides gives asymmetric induction in the product thiirane 1,1-dioxides. Thus, when thioformaldehyde S,S-dioxide, generated from methanesulfonyl chloride and triethylamine, is treated with optically active AM-phenylethyl-Af-methylpropanal enamine, a mixture of diastereomeric thietane 1.1-dioxides 6 is formed quantitatively. Removal of the chiral 1-phenylethyl auxiliary followed by Hoffmann elimination gives (-+ )-(5)-2-methyl-2//-thiete 1,1-dioxide (7) with 6% ee1,8. 

In two-phase systems, absorption of mierowave radiation by dieleetrie heating and ionic conduction enables individual phases to be heated at different rates, potentially affording sizable temperature differenees. Raner et al. (1995) performed a Hoffmann elimination using a two-phase water-chloroform system The reaction carried out in water at 105 °C led to polymerization of the final product. However, the reaction proceeds adequately under microwave irradiation in a two-phase water-chloroform system. The temperatures of the aqueous and oiganie phases were 110... 

Consider the elimination reaction below, which uses a strong, sterically hindered base (LDA). The product will be a double bond. This reaction will produce the Hoffmann product. Draw this product. 

So, if we look back at the reaction above, we find that the two possible products are monosubstituted and disubstituted double bonds. Whenever you have an elimination reaction where more them one possible double bond can be formed, we have names for the different products based on which one is more substituted and w hich one is less substituted. The more substituted product is called the Zaitsev product, and the less substituted product is called the Hoffmann product. Usually you get the Zaitsev product, but under special circumstances you can get the Hoffman product. If you use a strong, sterically hindered base, you can form the Hoffman product. 

As CO is highly toxic, and causes respiratory problems, its elimination is quite important Industrially, CO elimination is required for C02 laser application, and the production of pure hydrogen for fuel cells. Catalysis testing of the reaction has been performed, independently, with an IR gas-sensor by Hoffmann et al. and with a combustible CO gas sensor by Yamada et al. [25, 26]. In both groups, C02 produced by CO oxidation was quantified by an IR gas-sensor. 

The C5 aldehyde intermediate is produced from butadiene via catalytic oxidative acetoxylation followed by rhodium-catalyzed hydroformylation (see Fig. 2.30). Two variations on this theme have been described. In the Hoffmann-La-Roche process a mixture of butadiene, acetic acid and air is passed over a palladium/tellurium catalyst. The product is a mixture of cis- and frans-l,4-diacetoxy-2-butene. The latter is then subjected to hydroformylation with a conventional catalyst, RhH(CO)(Ph3P)3, that has been pretreated with sodium borohydride. When the aldehyde product is heated with a catalytic amount of p-toluenesulphonic acid, acetic acid is eliminated to form an unsaturated aldehyde. Treatment with a palladium-on-charcoal catalyst causes the double bond to isomerize, forming the desired Cs-aldehyde intermediate. 

Structure 4 is an intermediate for manufaeturing vitamin A (Scheme 2). The annual demand for vitamin A is about 3000 tons. Major producers are BASF, Hoffmann-La Roche and Rhone-Poulenc Animal Nutrition [55]. At an early stage in the synthesis BASF and Hoffmann-La Roche are using a hydroformylation step to synthesize 4 starting from l,2-diacetoxy-3-butene (5) and 1,4-di-aeetoxy-2-butene (6), respectively [56, 57]. The selectivity toward the branched product in the BASF process is achieved by using an unmodified rhodium carbonyl catalyst at a high reaction temperature. The symmetry of 6 in La Roche s process does not lead to regioselectivity problems. Elimination of acetic acid and isomerization of the exo double bond (La Roche) yields the final product 4 in both processes. 

The 8.4 eV photodecomposition of cyclopentene was also studied in the same laboratory. Ethylene, acetylene, and cyclopentadiene are the major products, although a high yield of hydrogen atoms was also observed (94). On the other hand, methylenecyclobutane (d> = 0.04) and bicyclo[2. l.Ojpentane (d> = 0.03) were the only primary products observed in the 184.9 nm photochemistry of n-heptane solution of cyclopentene (95). The formation of 1,4-pentadiene (d> = 0.01) was ascribed to secondary processes. Very recently we have undertaken a systematic study of the 184.9 nm gas phase photochemistry of cyclopentene at pressures from 1 Torr to 6 atm of added propane. Again at low pressure, ethylene (d> = 0.12), acetylene (d> = 0.03), allene (d> = 0.06), and cyclopentadiene (d> = 0.22) are the main products (96). About 80% of the formation of cyclopentadiene involves the elimination of a hydrogen molecule in agreement with the Woodward-Hoffmann allowed 1,4 concerted molecular elimination process (97). Moreover, several isomers are also formed provided... 

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