Crotyl diazoacetate

CROTYL DIAZOACETATE (Acetic acid, diazo-, [Pg.12]

C. Crotyl diazoacetate. A solution of 10.0 g. (0.038 mole) of the />-toluenesulfonylhydrazone of glyoxylic acid chloride in 100 ml. of methylene chloride is cooled in an ice bath. Crotyl alcohol (2.80 g. or 0.038 mole) (Note 7) is added to this cold solution, and then a solution of 7.80 g. (0.077 mole) of redistilled triethyl-amine (b.p. 88.5-90.5°) in 25 ml. of methylene chloride is added to the cold reaction mixture dropwise and with stirring over a 20-minute period. During the addition a yellow color develops in the reaction mixture and some solid separates near the end of the addition period. The resulting mixture is stirred at 0° for 1 hour and then the solvent is removed at 25° under reduced pressure with a rotary evaporator. A solution of the residual dark orange liquid in approximately 200 ml. of benzene is thoroughly mixed with 100 g. of Florisil (Note 8) and then filtered. The residual Florisil, which has adsorbed the bulk of the dark colored by-products, is washed with two or three additional portions of benzene of such size that the total volume of the combined benzene filtrates is 400-500 ml. This yellow benzene solution of the diazoester is concentrated under reduced pressure at 25° with a rotary evaporator, and the residual yellow liquid is distilled under reduced pressure. (Caution This distillation should be conducted in a hood behind a safety shield) (Note 9). The diazo ester is collected as 2.20-2.94 g. (42-55%) of yellow liquid, b.p. 30-33° (0.15 mm.), n T) 1.4853 - 1.4856 (Note 10). 

Coupling, reductive, of o-chlorobenzal-dehyde by hexamethylphosphor-ous triamide to give 2,2 -di-chloro-a,a -epoxybibenzyl, 46, 31, -Cresol, 48, 96 -t-Crotonolactone, 46,22 Crotyl diazoacetate, 49, 22, 24 Cupric acetate in coupling of phenyl-acetylene, 46, 39... 

Crotyl diazoacetate has been prepared by the procedure described here and by the reaction of diazomethane with crotyl chloroformate. The lower homolog, allyl diazoacetate, has been )repared by the reaction of allyl glycinate with nitrous acid and by the successive conversion of allyl chloroacetate to the corresponding azide, iminophosphorane, and, finally, the diazo ester. ... 

Crotyl diazoacetate has been prepared by the procedure described here and by the reaction of diazomethane with crotyl chloroformate. The lower homolog, aUyl diazoacetate, has been... 

The reaction of crotyl bromide with ethyl diazoacetate once again reveals distinct differences between rhodium and copper catalysis. Whereas with copper catalysts, the products 125 and 126, expected from a [2,3] and a [1,2] rearrangement of an intermediary halonium ylide, are obtained by analogy with the crotyl chloride reaction 152a), the latter product is absent in the rhodium-catalyzed reaction at or below room temperature. Only when the temperature is raised to ca. 40 °C, 126 is found as well, together with a substantial amount of bromoacetate 128. It was assured that only a minor part of 126 arose from [2,3] rearrangement of an ylide derived from 3-bromo-l-butene which is in equilibrium with the isomeric crotyl bromide at 40 °C. 

The Rh2(OAc)+-catalyzed reaction between crotyl bromide and ethyl diazoacetate at or below room temperature follows the pathway 129 - 131 - 132 exclusively. At higher temperature, when ethyl bromoacetate and increasing amounts of the [1,2] rearrangement product 126 are found additionally, the 129 -> 130 - 132 -f 133 route becomes a competing process. With copper catalysts, this situation may be applicable at all temperatures, but it has been suggested that the route via complex 130 operates solely, when copper bronze is the catalyst154). 

The substitution pattern in the product obtained through this sequence was in agreement with the proposed mechanism (Table 3.7). For example, crotyl chloride gave the 2-chloro-3-methyl hex-4-enoates (entries 3 and 4), and propargyl bromides gave the allenic products (e.g., entries 7 and 8). Yields were usually better with the more substituted tert -butyl diazoacetate. 

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