Dehydration with methyl group

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

Without exception the 17-secondary alcohols give three products, the dehydration products with migration of the 13j5-methyl group, the 17a-fluoro derivatives and the 17/5-chlorofluoroacetates. ... 

Dehydration of (8) with dilute methanolic potassium or sodium hydroxide at reflux is accompanied by inversion of the C-6 methyl group to the 6a-configuration to give (9).i36-i40... 

Bromination of the methyl group of (249) with A -bromosuccinimide, followed by reaction with excess secondary amine gave (250) which shows combined analgesic and antitussive properties. The Reformatsky reaction has also been used for the preparation of 2-amino-ethyl 3,3-diaryl-3-hydroxypropanates (251) as well as their dehydration products. The propene amides (252) have also been prepared for pharmacological evaluation. In l-methyl-3-bis (2-thienyl)-... 

The role of the trimethylsilyl group is to stabilize the enolate formed in the conjugate addition. The silyl group is then removed during the dehydration step. Methyl 1-trimethylsilylvinyl ketone can be used under aprotic conditions that are compatible with regiospecific methods for enolate generation. The direction of annulation of unsymmetrical ketones can therefore be controlled by the method of enolate formation. 

The dehydration of neopentyl alcohol can best be explained by a concerted mechanism involving the removal of the proton from the y-carbon atom by the basic sites and of the hydroxyl group by the acid sites of the alumina, with migration of the methyl group ... 

Davis studied the dehydration of urea nitrates as a route to iV-nitroureas. The nitrate salt of iV-methylurea undergoes dehydration-rearrangement on treatment with concentrated sulfuric acid to give Af-nitro-A -methylurea in 42 % yield. In this compound the nitro and methyl groups are attached to the same nitrogen and so its hydrolysis can provide a route to methylnitramine. In contrast, the nitrate salts of ethyl, n-propyl, n-butyl and n-amyl ureas, give iV-nitro-A -ethylurea (49 %), A -nitro-A -propylurea (60 %), iV-nitro-iV -butylurea (67 %) and iV-nitro-A -amylurea (67 %), respectively, on treatment with concentrated sulfuric acid. 

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