Enecarbamates, addition with

Beak and co-workers have also produced the key alcohol intermediate 74 by the sparteine-mediated lithiation and conjugate addition of allylamines to nitroalkenes to give Z-enecarbamates in good yields with high enantio- and diastereoselectivty (Scheme 16). Thus treatment of the allylamine 87 with n-BuLi in the presence of (-)-sparteine followed by conjugate addition to nitroalkene 88 gave the desired enecarbamate 89 in... 

As shown in Scheme 33, the synthesis of the C1-C7 amide 160 began with a Hoppe crotyltitanation reaction between the aldehyde 17 and the (R)-crotyltitanium 163, prepared in situ (crotyl diisopropylcarbamate with sBuLi/(-)-sparteine/ Ti(0/Pr)4), to give O-enecarbamate 164 (>30 ldr) [166-169], Ozonolysis and HWE chain extension was followed by an Evans-Prunet 1,4-addition to install the C5-stereocentre to complete 160 [103], The synthesis of the C8-C14 subunit 161 started with an elegant installation of the C13-C14 (Z)-olefin. Deprotonation of the dihydrofuran 165, available in three steps from bromo alcohol 166, with fBuLi and transmetallation with Me2CuLi LiCN, and subsequent 1,2-cuprate transfer gave the... 

In addition to heterolysis of compounds of type (2), N-acyliminium intermediates (1) are also obtained by protonation of Af-acylimines (27) and by protonation of enamides or enecarbamates (28). The former method is mainly of theoretical interest, Ixcause /V-acylimines (27) are rather unstable compounds. The latter technique is occasionally applied, although compounds (28) are usually synthesized through elimination of HX from (2). Other preparatively very useful methods for the in situ generation of the N-acyliminium ion are the acid-mediated coupling of an aldehyde (or ketone) with a primary (or secondary) amide or a nitrile, and the thermal reaction between an acid chloride and an imine. ... 

Despite their scarcity, asyrmnetric additions to electron-rich alkenes have also appeared in the literature. For example, Terada and coworkers [48a] reported the first enantioselective Friedel-Crafts reaction of enecarbamates 141 catalyzed by (R)-BINOL-derived monophosphoric acid 142 [49] (Scheme 10.28). This method provided an efficient access to highly enantioenriched 1-indolyl-l-alkylamine derivatives that have pharmaceutical and biological importance. Notably, the geometric isomers 141(Z) and 141( ) afforded the optical active amine 143 with the almost same... 

Enecarbamate [165] turned out to be an efficient nucleophile in the phosphoric acid catalyzed aza ene-type addition reaction to aldimines. It is noted that as low as 0.1 mol% of the catalyst (41f) worked well to give adducts with high yields and excellent enantioselectivity (Scheme 2.93) [166]. 

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