Synthesis of modified Weinreb amides: N-tert-butoxy-N-methylamides as effective acylating agents

Synthesis of α‐Amino Acids by Umpolung of Weinreb Amide Enolates

“…Instead, the main product from this reaction was amide 8 (Figure 1), the result of an undesired E2 pathway, together with N,O‐acetal 7a 14. In order to minimize the formation of the demethoxylated product 8 , the N ‐methoxy substituent in 4b was replaced by an N ‐ tert ‐butoxy moiety to give compound 4e ,15 and when this material was subjected to the same reaction conditions, the desired arylation product 5b could be isolated in 77 % yield (Entry 8). Simply decreasing the amount of base used resulted in an increased yield, allowing for 86 % of 5b (Entry 9).…”

Synthesis of Aryl Glycines by the α Arylation of Weinreb Amides

“…It has been shown previously that this type of elimination can be suppressed by using an N ‐ tert ‐butoxy substituent 11a. Thus, compound 6 b was selected as a suitable substrate and prepared in the same manner as amide 6 a , in this case from N ‐methyl‐ O ‐ tert ‐butylhydroxylamine hydrochloride ( 4 b ; Scheme ).…”

Chemical Synthesis of Brasilicardins

“…18 On the other hand, the sterically demanding O tert butyl Weinreb amide 31 was also synthesized from 29 via saponi cation and subsequent condensation of the resulting carboxylic acid with N methyl O tert butylhydroxylamine. 19 These two cyclization precursors, 30 and 31, were utilized in the ensuing B ring formation.…”