Alkyl formate production

Alkyl Formate Production. In the past few years, formate esters have become an important class of organic compounds mainly because of their versatility as chemical feedstock (16,36-42), and as raw materials for the perfume and fragrance industry (43-46). Specifically, formate esters (methyl, ethyl, pentyl, etc.) have been used as starting material for the production of aldehydes (36), ketones ( ), carboxylic acids (37-40), and amides ( ). For example, methyl formate can be hydrolyzed to formic acid (39,40) or catalytically isomerized to acetic acid ( ). On the other hand, alkyl formates have been employed in the perfume and fragrance industry in amounts of approximately 1000 to 3000 Ib/year (43—46). Among the formates that have been commonly used for these purposes are octyl ( ), heptyl ( ), ethyl ( ), and amyl ( ) formates. 

J-unsaturated ester is formed from a terminal alkyne by the reaction of alkyl formate and oxalate. The linear a, /J-unsaturated ester 5 is obtained from the terminal alkyne using dppb as a ligand by the reaction of alkyl formate under CO pressure. On the other hand, a branehed ester, t-butyl atropate (6), is obtained exclusively by the carbonylation of phenylacetylene in t-BuOH even by using dppb[10]. Reaction of alkynes and oxalate under CO pressure also gives linear a, /J-unsaturated esters 7 and dialkynes. The use of dppb is essen-tial[l 1]. Carbonylation of 1-octyne in the presence of oxalic acid or formic acid using PhiP-dppb (2 I) and Pd on carbon affords the branched q, /J-unsatu-rated acid 8 as the main product. Formic acid is regarded as a source of H and OH in the carboxylic acids[l2]. 

The formation of alkyl shifted products H and 14 can be explained in terms of the formation of endo-intermediate 21 formed by endo attack of bromine to 2 (Scheme 4). The determined endo-configuration of the bromine atom at the bridge carbon is also in agreement with endo-attack. Endo-Intermediate 21 is probably also responsible for the formation of cyclopropane products 12 and 15. The existence of cyclopropane ring in 12 and 15 has been determined by and 13c NMR chemical shifts and especially by analysis of cyclopropane J cH coupling constants (168 and 181 Hz). On the basis of the symmetry in the molecule 12 we have distinguished easily between isomers 12 and 15. Aryl and alkyl shift products IQ, H, and 14 contain benzylic and allylic bromine atoms which can be hydrolized easily on column material. 

Preparation of formamides from COz and a non-tertiary amine by homogeneous hydrogenation has been well studied and is extremely efficient (Eq. (12)). Essentially complete conversions and complete selectivity can be obtained (Table 17.3). This process seems more likely to be industrialized than the syntheses of formic acid or formate esters by C02 hydrogenation. The selectivity is excellent, in contrast to the case for alkyl formates, because the amine base which would stabilize the formic acid is used up in the synthesis of the formamide consequently little or no formic acid contaminates the product. The only byproducts that are likely to crop up in industrial application are the methylamines by overreduction of the formamide. This has been observed [96], but not with such high conversion that it could constitute a synthetic route to methylamines. 

Successive treatments of chiral acylsultam 50 with -BuLi or NaHMDS and primary alkyl halides, followed by crystallization, give the pure a,a-alkylation product 52 (Scheme 2-28). Under these conditions, the formation of C-10-alkylated by-product is inevitable. It is worth mentioning, however, that product 52 can readily be separated from the C(a)-epimers by crystallization. In fact,... 

Figure 10. A rearrangement of the silyl-alkyl insertion products leads to the formation of two distinct rj 3-silyl-allyl intermediates (syn and anti).

Several reports have described the formation of alkyl formates or form-amides from C02, hydrogen, and an alcohol or amine. The earlier catalytic preparations have been reviewed (108). A recent paper describes the production of alkyl formates catalyzed by several transition metal complexes and tertiary amines under 25 atm each of C02 and H2 at 140°C, (78) (159). 

It should be noted that the production of formic acid from C02 and H2 proceeds with a net increase in free energy under ambient conditions, but that an increased pressure of H2 and C02 will shift the equilibrium favorably. When alkyl formates or formamides are produced from C02, H2, and the amine or alcohol, the stability of the water formed in the reaction provides a powerful driving force, and the thermodynamics of these reaction are favorable under ambient conditions. 

Several groups have been successful at the catalytic conversion of carbon dioxide, hydrogen, and alcohols into alkyl formate esters using neutral metal - phosphine complexes in conjunction with a Lewis acid or base (109). Denise and Sneeden (110) have recently investigated various copper and palladium systems for the product of ethyl formate and ethyl formamide. Their results are summarized in Table II. Of the mononuclear palladium complexes, the most active system for ethyl formate production was found to be the Pd(0) complex, Pd(dpm)2, which generated 10/imol HCOOEt per /rniol metal complex per day. It was anticipated that complexes containing more than one metal center might aid in the formation of C2 products however, none of the multinuclear complexes produced substantial quantities of diethyl oxalate. 

A-10. The reaction of 3-methyl-l-butene with hydrogen chloride gives two alkyl halide products one is a secondary alkyl chloride and the other is tertiary. Write the structures of the products, and provide a mechanism explaining their formation. 

No products of disproportionation have ever been observed in the studies of Katzer s and Satterfield s groups, probably because either these products would be too heavy to desorb and thus to be detected, or steric hindrance due to the second ring, absent in the pyridine-piperidine reactions, prevents the alkyl transfer. However Schultz et al.33 found alkyl addition products, but did not specify whether these were A-alkyl or C-alkyl molecules. The formation of C-alkyl products will be shown later with the low pressure reaction. 

The 4-methoxy-l,2,3,4-tetrahydropyridine 224 undergoes thermal [2+2] cycloaddition to ethyl propiolate to give 1,6,7,8-tetrahydroazocine 225 which can be isomerized under acidic reducing conditions to 1,2,7,8-tetrahydroazocine 226 with concomitant elimination of methanol (Scheme 58) <2000TL6067>. Replacement of sodium borohydride with an alkyl Grignard reagent in the isomerization procedure results in formation of 2-alkyl-substituted products <2005EJ01052>. 

The selective oxidation of alkanes represents one of the most important and difficult challenges in the chemical industry, and significant recent attention has focused on the use of electrophilic late-transition-metal catalysts to achieve this goal [105-109]. These reactions are often performed in strong-acid solvents that enhance the electrophilicity of the metal center. The use of these solvents also results in formation of alkyl ester products that are deactivated toward further C - H oxidation. 

Skeletal Cu-Zn catalysts show great potential as alternatives to coprecipitated Cu0-Zn0-Al203 catalysts used commercially for low temperature methanol synthesis and water gas shift (WGS) reactions. They can also be used for other reactions such as steam reforming of methanol, methyl formate production by dehydrogenation of methanol, and hydrogenolysis of alkyl formates to produce alcohols. In all these reactions zinc oxide-promoted skeletal copper catalysts have been found to have high activity and selectivity. 

Alkylation of aromatics occurs principally via electrophilic substitution of the aromatic ring. This process involves the attack of an electrophile, E+, on the aromatic ring, e.g. ArH, which serves as a nucleophile. The result of this attack is the formation of the alkylated aromatic product and a proton as shown below ... 

LE s and relatively small Isoparaffins are produced when heavy olefins are used as feedstock for alkylation. The products obtained when Isobutylene or 2,2,4-trl-methylpentene-1 Is used as the olefin for alkylation resulted In almost Identical products Including LE s and DflH s (6,19). Even heavier olefins produce LE s, and fragmentation Is obviously of major Importance. Degradation of TMP s or DMH s In the presence of sulfuric acid leads to the formation of significant, and even major amounts of Isobutane and LE s (7). Fragmentation reactions obviously must be occurring. 

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