Electroorganic chemistry. 60. Electroorganic synthesis of enamides and enecarbamates and their utilization in organic synthesis

Abstract

A variety of enecarbamates and enamides were synthesized from -methoxy carbamates and -methoxy amides prepared by anodic methoxylation of amine derivatives. Some new carbon-carbon bond-forming reactions and hydroxylation at the ß position of amines have been accomplished by using these enecarbamates and enamides as key intermediates. Also, new synthetic routes of nicotinaldehyde and pyrrole derivatives have been exploited by utilizing anodic dimethoxylation of carbamates of piperidine and pyrrolidine, respectively.

Ring Contraction of α,β-Unsaturated Cyclic Amines with cis-Dihydroxylation at the α,β-Position

“…Starting from readily commercially available cyclic amines 4a-f, we activated the α-position by electrochemical oxidation in methanol 5 followed by acid catalyzed removal of methanol to afford α,β-unsaturated cyclic amines 1a-f. 6,7 These results are summarized in Table 1. 4a 4b 4c 4d 4e 4f 2 3 5 3 4 3 1a 1b 1c 1d 1e 1f 96 95 70 96 95 87 Having successfully prepared 1a-f, we embarked on the task of functionalizing and subsequent ring opening of the product 2a-f. First, dihydroxylation of 1a-f using OsO 4 followed by thermodynamically induced ring opening by use of elevated temperatures afforded 3a-f.…”

“…Compounds 1a, 12 1b, 13 1c, 6 and 1f 14 are known compounds. Recrystallization from AcOEt and n-hexane gave white crystalline compounds 3a,b,d,e.…”

Anodic Selective Functionalization of Cyclic Amine Derivatives

“…Lewis acid As shown in Scheme 2, removal of alcohols from N,O-acetals B generated enamine derivatives E which reacted with electrophiles to afford β-substituted enamines F. 10 Anodic oxidation of E in acetic acid gave α,β-diacetoxylated amines G which were directly obtained from amines A by anodic oxidation in acetic acid. Lewis acid promoted nucleohilic substitution gave β-acetoxy-α-substituted amines H. amines M (Nu=Ar) were easily shifted to the β-position by Ag + (Scheme 3).…”

Síntese de enaminonas

“…N-acil-enaminonas cíclicas do tipo E também podem ser produzidas por formilação ou acetilação de enamidas, nas condições das reações de Vilsmeier ou de Friedel-Crafts, respectivamente 123 (Esquema 24, eq. 26).…”