Butyl Carbazate

Submitted by Louis A. Carpino, David Collins, Siegfried Gowecke, Joe Mayo, S. D. Thatte, and Fred Tibbetts 1 Checked by Fred G. H. Lee and Virgil Boekelheide 

Cautionl Methyl chlorotkiolformate has an obnoxious odor. All operations should be conducted in a well-ventilated hood. 

t-Butyl S-methylthiolcarbonate. In a 5-1. round-bottomed flask, fitted with mechanical stirrer, reflux condenser, and dropping funnel are placed 430 ml. (422 g., 5.33 moles) of pyridine, 508 ml. (395 g., 5.33 moles) of Z-butyl alcohol, and 1.61. of chloro- 

The pyridine was a pure product, b.p. 113-115°, obtained from the Mallinckrodt Chemical Company. /-Butyl alcohol, m.p. 24.5-25.5°, and chloroform (u.s.p. or reagent grade) were obtained from the Matheson Company. All reagents were used as supplied. 

The methyl chlorothiolformate, b.p. 110-111°, was used as supplied by the Stauffer Chemical Company. 

---

A third approach to 3-amino-/3-lactams is by Curtius rearrangement of the corresponding acyl azides. These are readily prepared from r-butyl carbazides, available via photochemical ring contraction of 3-diazopyrrolidine-2,4-diones in the presence of f-butyl carbazate (c/. Section 5.09.3.3.2). Thus treatment of (201) with trifluoroacetic acid followed by diazotiz-ation gives the acyl azide (202) which, in thermolysis in benzene and subsequent interception of the resulting isocyanate with r-butanol, yields the protected 3-amino-/3-lactam (203) (73JCS(P1)2907). 

BUTYL CARBAZATE (Carbazic acid, tert-butyl ester)... 

Butyl carbazate has been prepared by reaction of hydrazine... 

Butyl carbazate, conversion to /-butyl hydrazodiformate, 44,18 /-Butyl chloride, 44, 102 ree-Butyl cinnamate, 41, 62 rec-Butyl crotonate, 41, 60 reaction with n-butyl Grignard reagent, 41, 61... 

In a 1-1. round-bottomed flask fitted with a mechanical stirrer are placed 82 g. (0.62 mole) of /-butyl carbazate,2 72 g. of glacial acetic acid, and 100 ml. of water. The solution is cooled in an ice bath, and 47.0 g. (0.68 mole) of solid sodium nitrite is added over a period of 40-50 minutes, the temperature being kept at 10-15° (Note 1). The mixture is allowed to stand in the ice bath for 30 minutes, 100 ml. of water is added, and the floating oil is extracted into four 40-ml. portions of ether. The combined ether extracts are washed twice with 50-ml. portions of water and with 40-ml. portions of lAf sodium bicarbonate solution until no longer acidic (about three washings are required). The solution is dried over magnesium sulfate, and the ether is removed by distillation from a water bath maintained at 40-45° water aspirator pressure of 140-150 mm. is used. The pressure is then... 

Butyl azidoformate has been prepared only from /-butyl carbazate.8 6... 

Butyl hydrazodiformate has been prepared by acylation of /-butyl carbazate by means of /-butyl azidoformate 3 4 or /-butyl cyanoformate.5 /-Butyl azodiformate has been prepared only by oxidation of the hydrazo compound. ... 

Butyl carbazate is also a key intermediate in the synthesis of /-butyl azidoformate,5 6 12 /-butyl hydrazodiformate, /-butyl azo-diformate,18 and /-butyl N-hydroxycarbamate,12 14 all of winch are valuable synthetic intermediates. 

HYDRAZINES t-Butyl carbazate. HYDRINDANES Zirconium(IV) n-propoxide. 

The kinetics of the gas-phase elimination of ethyl and /-butyl carbazates have been studied in a static reactor system over the temperature range 220.3-341.7 °C and pressure range 21.1-70.0 torr.13 Theoretical calculations on the thermal decomposition of ethyl carbazate (4) suggest that the reaction proceeds by a concerted non-synchronous mechanism, through a quasi-three-membered ring transition state (Scheme 4). In contrast, the transition state structure for the thermal decomposition of /-butyl carbazate is an almost planar six-membered ring. 

Butyl carbazate has been prepared by reaction of hydrazine with /-butyl phenyl carbonate,6-4 /-butyl S-methylthiolcarbonate,3... 

Butyl azodiformate, 44,18 a-Butyl bromide, preparation of -butyl Grignard reagent from, 41, 61 (-Butyl carbazate, 44, 20 conversion to (-butyl azidoformate, 44,15... 

An addition to the literature on the arylation of protected hydrazines was recently contributed by Skerlj et al. [186]. In addition to the reactions of halopyridines with tert-butyl carbazate (H2NNHBoc) discussed in Section 4.3.2.3, these authors have reported the reaction of electron-deficient aryl bromides with this substrate. Reactions occurred when using DPPF or the ferrocenyl 11 as the ligand along with CS2CO3 as the base at temperatures of 100-110 °C. 

OButyl azidoformate, a useful protective group for primary and secondary amino groups,4 0 has been prepared previously from f-butyl carbazate.3 The present procedure7 is a more convenient preparative method. 1 he intermediate carbonic phosphoric anhydride reacts with nucleophiles other than the azide ion in this preparation. Reaction of this anhydride with amines yields the t-butoxycarbonyl derivatives of amines.7 Other carbonic phosphoric anhydrides have been prepared by procedures analogous to the method described here.8... 

---