General Papers ARKIVOC 2006 (xi) 21-36
pivaloylation of primary alcohol over phenol was observed as demonstrated for substrate 48 (Table 8 and 9).
Table 8. Isobutyrylationa of alcohols, thiol and amines with (iPrCO)2O catalyzed by EDPBT
Substrate Product Time/min Yield (%)b CH3-(CH2)8CH2OH (1) CH3-(CH2)8CH2OCOiPr (1c) 20 89 Ph-(CH2)2CH2OH (3) Ph-(CH2)2CH2OCOiPr (3c) 20 92 Ph-CH(CH3)OH (16) Ph-CH(CH3)OCOiPr (16c) 30 88 PhCH=CHCH2OH (24) PhCH=CHCH2OCOiPr (24c) 15 80 C6H5-NH2 (41) C6H5-NHCOiPr (41c) 05 94 CH3(CH2)10CH2SH (46) CH3(CH2)10CH2SCOiPr (46c) 60 78c 4-OH-C6H4-CH2CH2OH (48) 4-OH-C6H4-CH2CH2OCOiPr (48c) 10 95
a Reactions were monitored by TLC. b Isolated yield. cCH3CN was used as the solvent Table 9. Pivaloylationa of alcohols and amines with (t-BuCO)2O catalyzed by EDPBT
Substrate Product Time/ min Yield (%)b CH3-(CH2)8CH2OH (1) CH3-(CH2)8CH2OCOt-Bu (1d) 60 86 Ph-(CH2)2CH2OH (3) Ph-(CH2)2CH2OCOt-Bu (3d) 60 90 Ph-CH(CH3)OH (16) Ph-CH(CH3)OCOt-Bu (16d) 90 80 PhCH=CHCH2OH (24) PhCH=CHCH2OCOt-Bu (24d) 90 89 C6H5-CH2-NH2 (39) C6H5CH2-NHCOt-Bu (39d) 15 88 4-OH-C6H4-CH2CH2OH (48) 4-OH-C6H4-CH2CH2OCOt-Bu (48d) 80 82
a Reactions were monitored by TLC. b Isolated yield
Benzoic anhydride, an aromatic anhydride reacted with alcohols, amines, and thiol to give corresponding benzoates (1e, 3e, 24e, 41e, 46e, 48e and 49e). The reaction of benzoic anhydride with various alcohols, amine and thiol is summarized in Table 10. In general, the more hindered the anhydride; the slower is the acylation rate. Notably, under the present reaction condition there is not much difference in the acylation rates of alcohols, amines and thiols with acetic, propionic and isobutyric anhydride but the reaction is slower for pivalic and benzoic anhydride. This observation is consistent with the observations made by others.21a,b
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