245674-32-2

Upstream product

• 181531-14-6 (R)-(+)-1-(2,4,6-triisopropylphenyl)ethanol 
• 616-45-5 2-pyrrolidinon 
• 245674-29-7 (1R)-1-(2,4,6-triisopropylphenyl)ethyl-1H-1-imidazolecarboxylate 

Downstream Products

• 245674-46-8 (1R)-1-(2,4,6-triisopropylphenyl)ethyl-2,3-dihydro-1H-1-pyrrolecarboxylate 
• 245674-42-4 (1R,2RS)-1-(2,4,6-triisopropylphenyl)ethyl-2-hydroxy-1-pyrrolidinecarboxylate 

Relevant academic research and scientific papers

Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (-)-Geissman-Waiss lactone

The diastereofacial selectivity of enecarbamates bearing a chiral auxiliary was evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeric azacyclobutanones derived from the 8-phenylmenthyl enecarbamate permitted an enantiodivergent synthesis of the (-)-Geissman-Waiss lactone, a key intermediate in the synthesis of necine bases.

Efficient and Expeditious Protocols for the Synthesis of Racemic and Enantiomerically Pure Endocyclic Enecarbamates from N-Acyl Lactams and N-Acyl Pyrrolidines

A mild, practical, and straightforward protocol for the construction of endocyclic enecarbamates starting from N-acyl lactams and N-acyl pyrrolidines is presented. Lactams were reduced to the corresponding α-hydroxycarbamates in good to excellent yields using DIBAL-H, SuperHydride, or NaBH4 followed by β-elimination (dehydration) promoted by trifluoroacetic anhydride in the presence of hindered nitrogenated bases such as 2,6-lutidine, diisopropylethylamine, or triethylamine. Small variations of this protocol permitted the preparation of several endocyclic enecarbamates (12 examples) in good to excellent overall yields (56-96%). The protocol was demonstrated to be applicable to several ring sizes, compatible with different protecting groups, and to be mild enough to prevent racemization of racemization-prone stereocenters. The efficacy of the procedure in the preparation of enantiomerically pure endocyclic enecarbamates was also demonstrated and compared to the commonly used Shono's protocol, which in our hands led to partial racemization of the endocyclic enecarbamate 18c.