Propionic 2-alkoxy-2-methyl

In 1997, the first truly catalytic enantioselective Mannich reactions of imines with silicon enolates using a novel zirconium catalyst was reported [9, 10]. To solve the above problems, various metal salts were first screened in achiral reactions of imines with silylated nucleophiles, and then, a chiral Lewis acid based on Zr(IV) was designed. On the other hand, as for the problem of the conformation of the imine-Lewis acid complex, utilization of a bidentate chelation was planned imines prepared from 2-aminophenol were used [(Eq. (1)]. This moiety was readily removed after reactions under oxidative conditions. Imines derived from heterocyclic aldehydes worked well in this reaction, and good to high yields and enantiomeric excesses were attained. As for aliphatic aldehydes, similarly high levels of enantiomeric excesses were also obtained by using the imines prepared from the aldehydes and 2-amino-3-methylphenol. The present Mannich reactions were applied to the synthesis of chiral (3-amino alcohols from a-alkoxy enolates and imines [11], and anti-cc-methyl-p-amino acid derivatives from propionate enolates and imines [12] via diastereo- and enantioselective processes [(Eq. (2)]. Moreover, this catalyst system can be utilized in Mannich reactions using hydrazone derivatives [13] [(Eq. (3)] as well as the aza-Diels-Alder reaction [14-16], Strecker reaction [17-19], allylation of imines [20], etc. 

Hydroxy-2-methyl-3-alkoxy- propionic acid residue 9 o... 

Large" and "small require definition at this point. What is important is the size of the group from the standpoint of the substituent attached to the a position relative to the carbonyl group. Thus, in propionate esters, all alkoxy groups are "small," since the methyl senses only the oxygen part of the group. 

The reactions of allylboronates with a-methyl-P-alkoxy aldehydes provides propionate adducts which are useful for the synthesis of polypropionate... 

Figure VII-B-26. Atmospheric fate of the alkoxy radicals formed during the atmospheric oxidation of methyl propionate A = 0CH20C(0)C2H5, B = CH30C(0)CH0CH3, C = CH30C(0)CH2CH20 (Cavalli et ah, 2000b).

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