Synthesis of Enol Carbonates from a Reaction of Silyl Enolates with 1H-Imidazolylurethane

Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters

“…We presume that the initial formation of the complex CDI→BF 3 ( 3 ) can take place in two different ways; either via an imidazolium intermediate ( 3A ), as was recently suggested by Ohta,28b or through coordination of the boron atom with the carbonyl oxygen ( 3B ) in a similar way as in the case of carbonyl derivatives (Chart ) 1 …”

“…Indeed, it is interesting to note that the reaction is general and applicable to all types of alcohols, including tertiary ones 28e. Thus, simple and reactive primary alcohols such as methanol or allyl alcohol (entries 2, 3, 21, 25, 26, and 28, Table ) or others including more complex structures such as terpenes, geraniol, (+)-menthol, or (−)-8-phenylmenthol (entries 11, 14, 17, and 29, Table ), steroids such as 5α-cholestane-3β-ol (entry 16, Table ), or protected carbohydrates such as 1,2;5,6-di- O -isopropylidene-α- d -glucofuranose (entry 15, Table ) were successfully used.…”

“…This ability has been mainly used in processes which imply formation of two carbon−heteroatom bonds. As examples we can mention the synthesis of chiral hydantoins, isocyanates, and unsymmetrically substituted carbonic acid derivatives 24a, and, more recently, the preparation of urea dipeptides …”

Simple Method for the Preparation of Esters from Grignard Reagents and Alkyl 1-Imidazolecarboxylates

“…A range of 1-imidazolecarboxylates 2 , which were prepared by the reactions of primary and secondary alcohols 1 with CDI (3 equiv) in THF, were obtained as analytically pure compounds in good to excellent yields after aqueous workup (Table ). The reaction of Grignard reagents 3 with the 1-imidazolecarboxylates 2 was optimized for the condensation of 1-imidazolecarboxylate 2a with phenylmagnesium chloride ( 3a ; Scheme ).…”