Carbamates Boron trifluoride etherate

Another AMPA-derived procedure took advantage of the neat reaction between the N-carbamoyl-HHT 59 and diethyl phosphite catalyzed by boron trifluoride etherate to generate the AMPA carbamate 60. Subsequent alkylation with ethyl bromoacetate and base produced the glyphosate triester carbamate 61, which was hydrolyzed to GLYH3 (59). 

The weak nucleophilic nature of polynitroaliphatic alcohols is also reflected in their slow reactions with isocyanates to yield carbamates. These reactions often need the presence of Lewis acids like ferric acetylacetonate or boron trifluoride etherate. The reaction of bifunctional isocyanates with polynitroaliphatic diols has been used to synthesize energetic polymers.33°... 

Carbamates Allyl chloroformate, 9 Boron trifluoride etherate, 43 t-Butyldimethylsilyl trifluoromethanesul-fonate, 50... 

When the reaction was carried out in chloroform in the presence of ethyl carbamate with boron trifluoride-etherate as catalyst, /J-ethoxycarbonylaminoalkyl phenyl tellurium oxides were formed. These tellurium oxides were not purified but reduced with hydrazine to the corresponding tellurium compounds. ... 

Treatment of lactam methyl ether (111 R = Me) with trialkylalanes, however, generated desired product (112) in modest yield (equation 14). Similarly, Shono et al. have treated a-methoxy carbamates (113) with Grignard reagents in the presence of boron trifluoride etherate to afford substituted pyrrolidines (114 equation IS). 

E)-a,p-Unsaturated aldehydes. The anion of 2-alkenyl N,N-diethyldithio-carbamates (2) reacts with (1) at the a-carbon atom to form a product (a) that undergoes facile [3,3] sigmatropic rearrangement to form (3). The products are hydrolyzed to aldehydes (4) by red mercuric oxide and boron trifluoride etherate (3,136). ... 

Cleavage of Benzyl Carbamates. The removal of the benzy-loxycarbonyl (Cbz) group from nitrogen can be achieved successfully using boron trifluoride etherate in the presence of either a thiol or dimethyl sulfide. The carbamates derived from secondary amines are cleaved more rapidly than those from primary amines using the ethanethiol method, even when using BF3-OEt2 as the solvent. The procedure allows reasonable selectivity, as shown in eq 11. ... 

The efficiently chelated (zinc chloride, boron trifluoride diethyl ether complex), rigid five-mem-bered-ring dienophiles la and lb have been used in the enantioselective syntheses of several natural products. Thus, the reaction of (S)-l with 1,3-butadiene (5), promoted by zinc chloride (1 equiv) produces the cycloadduct ( + )-6 (83% d.r. 99 1), later converted to a precursor of (S)-sarkomycin (7). Cycloaddition of (S)-la with l,4-diacetoxy-l,3-butadicnc (8), catalyzed by boron trifluoride-diethyl ether complex (0.5 equiv) gives (-)-9 (72%) as a single diastercomer, further converted into (-)-shikimic acid (10) in a six-step procedure. Similarly, addition of (/ )-lb to 1,3-butadiene carbamate 11 in the presence of boron trifluoride-diethyl ether complex (1 equiv) produces ( + )-12 (95% d.r. 99 1), which was converted into ( + )-pumiliotoxin. 

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