Benzotriazole-Mediated Conversions of Aromatic and Heteroaromatic Aldehydes to Functionalized Ketones
摘要:
Aromatic and heteroaromatic aldehydes reacted with benzotriazole and triethyl orthoformate in THF to give the corresponding alpha-(benzotriazol-1-yl)aryl ethyl ethers 7 in good yield. The novel acyl anion precursors 7 underwent smooth lithiation at the methine group followed by trapping with alkyl halides, aldehydes, ketones, and imines to yield the expected substituted intermediates of type 9, which were hydrolyzed under mild conditions without isolation. Benzaldehyde, methyl-, chloro-, and methoxy-substituted benzaldehydes, 1-naphthalenecarboxaldehyde, 2- and 3-furaldehydes, 2- and 3-thiophenecarboxaldehydes, and 2-pyridinecarboxaldehyde were all transformed in this manner into a variety of aryl and heteroaryl ketones with alkyl (10), alpha-hydroxyalkyl (12 and 13), alpha-aminoalkyl (14) and acyl(15) substituents.
Acylboranes are among the most elusive boron-containing organic functional groups, a fact that has impeded development of new reactions employing them as substrates. A new synthesis of acyltrifluoroborates from benzotriazole (Bt)-based N,O-acetals has been developed. Two other routes provide acyltrifluoroborates containing alcohols, aldehydes, and carbamates. The ketone-like reactivity of the acyltrifluoroborate functional group is demonstrated, and the first X-ray structure of an acyltrifluoroborate is reported.
Preparation of 1,2- and 1,4-diols via selective cleavage of C-benzotriazole bonds in reductive lithiations of N-(α-alkoxy-benzyl- and -allyl-)benzotriazoles
作者:Alan R. katritzky、Weiliang Bao、Ming Qi、Clara N. Fali、Indra Prakash
DOI:10.1016/s0040-4039(98)01390-2
日期:1998.9
Selective cleavage of C-benzotriazole bonds in the presence of C-O bonds is reported for the reductive lithiation of N-(alpha-alkoxybenzyl)benzotriazoles and N-(alpha-alkoxyallyl)benzotriazoles in a one-step or two-step process. Trapping of the intermediates with carbonyl compounds gave unsymmetrically protected 1,2 or 1,4-diols in moderate yields. (C) 1998 Elsevier Science Ltd. All rights reserved.