Primary, secondary, and tertiary with no catalyst

This valuable method utilizes the O-TMS enol ethers derived from either pentane-2,4-dione or methyl acetoacetate, the former being the more reactive. Even t-alcohols are rapidly and quantitatively silylated in DMF at room temperature. A similar technique can be used to introduce the TBDMS group, although here ptsa catalysis is required (4). 

4-Trimethylsilyloxypent-3-en-2-one (20.2 mmol) was added to a solution of the alcohol (20mmol) in DMF (20ml). After being shaken for 10min, the mixture was extracted with pentane (5 x10 ml). The combined organic extracts were washed with cold water (4x 10ml), dried and concentrated. 

The use of HMDS (ca. 1.5 mmol) and saccharin (0.01 mmol) per mmol of substrate in refluxing dichloromethane or chloroform has been recommended (5) for easy silylation of carboxylic acids, including azetidin-2-one-4-carboxylic acids. Clear solutions result, i.e., no ammonium salts are present at completion of the reaction, and consequently the silyl esters can be obtained by direct distillation, or merely by evaporation of solvent. 

To a suspension of (4S)-azetidin-2-one-4-carboxylic acid (0.1 mol) and saccharin (1 g) in chloroform (200ml) was added HMDS (0.4 mol), and the mixture was heated under reflux for 1.5 h. The excess HMDS was removed under reduced pressure, and the residue was distilled to afford the protected /3-lactam (0.089 mol. 89%). b.p. 74-76 °C/0.08mmHg. 

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The first step of the activation of butane and cyclohexane has been assumed to be the cleavage of a secondary C—H bond, with minor contributions from primary C — H bonds in the case of butane. This picture is supported only by indirect evidence. When the relative rates of reaction of various alkanes were compared on a V-Mg oxide and Mg2V207 catalyst (Table VIII), it was found that alkanes with only primary carbons (ethane) reacted most slowly. Those with secondary carbons (propane, butane, and cyclohexane) reacted faster, with the rate being faster for those with more secondary carbon atoms. Finally, the alkane with one tertiary carbon (2-methylpropane) reacted faster than the ones with either a single or no secondary carbon (26). From these data, it was estimated that the relative rates of reaction of a primary, secondary, and tertiary C—H bond in alkanes on the V-Mg oxide catalyst were 1, 6, and 32, respectively (26). 

Reaction with Nitrogen Nucleophiles. The acid-catalyzed reaction of primary, secondary, and tertiary amines with ethyleneimine yields asymmetrically substituted ethylenediamines (71). Steric effects dominate basicity in the relative reactivity of various amines in the ring-opening reaction with ethyleneimine (72). The use of carbon dioxide as catalyst in the aminoethylation of aliphatic amines, for which a patent application has been filed (73), has two advantages. First, the corrosive salts produced when mineral acids are used as catalysts (74,75) are no longer formed, and second, the reaction proceeds with good yields under atmospheric pressure. 

Alcohols undergo dehydration in supercritical and hot water (41). Tertiary alcohols require no catalyst, but secondary and primary alcohols require an acid catalyst. With 0.01 MH2SO4 as a catalyst, ethanol eliminates water at 385°C and 34.5 MPa to form ethene. Reaction occurs in tens of seconds. Only a small amount of diethyl ether forms as a side reaction. 

The results show that a number of ruthenium carbonyl complexes are effective for the catalytic carbonylation of secondary cyclic amines at mild conditions. Exclusive formation of N-formylamines occurs, and no isocyanates or coupling products such as ureas or oxamides have been detected. Noncyclic secondary and primary amines and pyridine (a tertiary amine) are not effectively carbonylated. There appears to be a general increase in the reactivity of the amines with increasing basicity (20) pyrrolidine (pKa at 25°C = 11.27 > piperidine (11.12) > hexa-methyleneimine (11.07) > morpholine (8.39). Brackman (13) has stressed the importance of high basicity and the stereochemistry of the amines showing high reactivity in copper-catalyzed systems. The latter factor manifests itself in the reluctance of the amines to occupy more than two coordination sites on the cupric ion. In some of the hydridocar-bonyl systems, low activity must also result in part from the low catalyst solubility (Table I). 

Coupling reactions between C(5p )-organometallics, mostly Grignard reagents, and C(sp ) halides and related compounds are usually achieved with Cu catalysts. Primary alkyl halides react smoothly, secondary alkyls are applicable in only a few cases, and no successful coupling has been reported for tertiary alkyl halides. Allylic halides and related compounds are treated separately, since there are important regiochemical problems. 

The results of catalysis with primary and secondary amines indicate that ruthenium carbonyl forms active catalysts in aqueous ethylenediamines, diethanolamine, pyrrolidine and piperidine solutions. No detectable amounts of hydrogen are formed with aromatic and unsaturated primary and secondary amines under the present WGS conditions. Tertiary amines were found not to initiate catalyst systems as active as those produced by the best primary and secondary amines. Aliphatic tertiary amines exhibited only weak activity. 

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