Hydrogen with rearrangement

Hydride shift (Section 5 13) Migration of a hydrogen with a pair of electrons (H ) from one atom to another Hydnde shifts are most commonly seen in carbocation rearrange ments... 

This method of preparation is suitable for producing primary alkyl lactates but is unsatisfactory for /3-methallyl lactate because the strong mineral acid catalyzes the rearrangement of methallyl alcohol to isobutyraldehyde. Methyl lactate can be made conveniently (80-85% yield) by heating 1 mole of lactic acid condensation polymer with 2.5-5 moles of methanol and a small quantity of sulfuric acid at 100 for 1-4 hours in a heavy-walled bottle, such as is used for catalytic hydrogenation with a platinum catalyst. 

C-Nitroso compounds with an a-hydrogen atom rearrange readily to the corresponding oxime (/7y) and perhaps to the unsaturated hydroxylamine 145). Reduction of these is discussed in the chapter on oximes. 

A mixture of exo- and endo-isomers of 5-methylbicylo[2.2.1]hept-2-ene is hydrogenated with the aid of five equivalents of triethylsilane and 13.1 equivalents of trifluoroacetic acid to produce a 45% yield of < <7o-2-methylbicylo[2.2.1] heptane (Eq. 71). The same product is formed in 37% yield after only five minutes. The remainder of the reaction products is a mixture of three isomeric secondary exo-methylbicylo[2.2.1]heptyl trifluoroacetates that remains inert to the reaction conditions. Use of triethylsilane-l-d gives the endo-2-methylbicylo-[2.2.1]heptane product with an exo-deuterium at the tertiary carbon position shared with the methyl group. This result reflects the nature of the internal carbocation rearrangements that precede capture by the silane.230... 

Cleavage is often associated with elimination of small, stable, neutral molecules, such as carbon monoxide, olefins, water, ammonia, hydrogen sulfide, hydrogen cyanide, mercaptans, ketene, or alcohols, often with rearrangement (Section 2.8). 

The method of choice for adding hydrogen fluoride to oxiranes is the use of boron trifluoride-diethyl ether complex without added hydrogen fluoride. The reaction proceeds with rearrangements to yield the desired fluorohydrins and other byproducts. In some cases the ratio of products depends strongly on the reaction conditions used. 

Curtius rearrangement of the acyl azide of Ac-Phe-OH 31, at rt in dilute HC1, provided Ac-Phe-NH2-HC1 32 in up to 65% yield. Coupling of Z-Phe-OH with 32 using the mixed anhydride method afforded Ac-Pheip[NHCO]Phe-Z 33 as a single diastereomer in 55% yield. Reaction of 33 after hydrogenation with HCOCH(iPr)C02Me provides 34. Compound 34 was hydrogenated to afford the reduced-retro pseudotripeptide 35 in 65% yield for the two steps. 

Clays Lose structural OH groups with rearrangements of structure and release of h2o Ash weighs less than MM yield of water increases apparent organic hydrogen, oxygen, and VM... 

The chemistry of the 2-vinyl-l,3-thiazetidines 98 is interesting because these compounds undergo rearrangement to the thiazolidines 99 on catalytic hydrogenation and rearrangement to the thiazines 100 on treatment with Wilkinson s catalyst (Scheme 29) <1999J(P1)3569>. 

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