A practical synthesis of carbamates using an 'in-situ' generated polymer-supported chloroformate

Tetrahedron Letters

Volumn 45, Issue 37, 2004, Pages 6831-6834

  Mormeneo, David ^a,b   Llebaria, Amadeu ^b   Delgado, Antonio ^a,b  

^a UNIVERSITY OF BARCELONA   (Spain)

^b Inst da'Investigacions Q   (Spain)

Author keywords

Carbamates; Parallel synthesis; Phosgene equivalent; Solid phase; Supported reagents

Indexed keywords

ALCOHOL; AMINE; CARBAMIC ACID DERIVATIVE; CARBONIC ACID DERIVATIVE; PHOSGENE; POLYMER; RESIN;

ARTICLE; CARBON NUCLEAR MAGNETIC RESONANCE; HIGH PERFORMANCE LIQUID CHROMATOGRAPHY; PROTON NUCLEAR MAGNETIC RESONANCE; SYNTHESIS;

EID: 4344563934     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2004.07.124     Document Type: Article

References (26)

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24. Initial experiments showed, in some cases, a nonnegligible formation of the corresponding symmetrical ureas. We have attributed this side reaction to the incomplete formation of carbonates 2 from chloroformate 4, which depends on the intrinsic reactivity of the alcohol used. In agreement with this assumption, ureas were not observed from the sequential reaction of resin 1 with chloroformates and amines (Table 1), a process that does not imply the formation of chloroformate 4. The use of DMAP as catalyst for the synthesis of carbonates 2 from chloroformate 4 was crucial to avoid the formation of the urea byproducts
25. 2 (5 x 3 mL). The combined filtrates were washed with aqueous 1 N HCl (3 x 1.5 mL), dried, and evaporated to furnish carbamate 3e (27.3 mg, 88%). For NMR data, see Ref. 9
26. In a single case, carbamate 3a (Table 1) was obtained in comparable yield by using only 1.1 equiv of the corresponding amine. However, the generality of this modification has to be confirmed. Usually, excess reagents are recommended for parallel synthesis protocols