An Improved Preparation of Ethyl 2-Oxo-3-Pyrrolidinecarboxylate

Control of End Groups in Anionic Polymerizations Using Phosphazene Bases and Protic Precursors As Initiating System (XH-ButP4 Approach): Application to the Ring-Opening Polymerization of Cyclopropane-1,1-Dicarboxylates

“…35,36 Soft bases such as organocuprates, thiolates or azides open the cyclopropyl ring, and are theoretically good candidates as initiators. [36][37][38][39] The first experiment summarized in Table 1 (entry 4) involved an aliphatic bifunctional initiator of the SH-type, i.e., bis(2-mercaptoethyl) ether O(CH 2 CH 2 SH) 2 . Full conversion was obtained with a high initiator efficiency and a low polydispersity for the polymer.…”

“…As a cyclopropanedicarboxylate monomer displays two sites for nucleophilic attack, i.e., the CH 2 on the cyclopropane ring (inducing a ring-opening by nucleophilic substitution on the carbon) and the carbonyl groups (inducing a nucleophilic addition), two types of adducts can be expected in the initiation step, depending on the regioselectivity of the attacking species. As a rule of thumb, hard bases such as Grignard reagents and alcoholates attack the ester functions preferentially and must be avoided as prospective initiators. , Soft bases such as organocuprates, thiolates or azides open the cyclopropyl ring, and are theoretically good candidates as initiators. − …”

Ring Opening of Donor–Acceptor Cyclopropanes with N-Nucleo­philes

“…156 The reaction between 1а and sodium azide required prolonged heating in N-methyl-2-pyrrolidone with triethylamine hydrochloride (Scheme 108). In the absence of Et 3 N·HCl, 1а was not converted into 190.…”

Termination of Mn(III)-Based Oxidative Cyclizations by Trapping with Azide

“…Equally good results were obtained in MeOH with α-methyl-substituted β-keto ester 3 , which affords 50% of azide 8a and 14% of epimeric azide 8b (Scheme ). The structures were established by hydrogenation (50 psi) of the crude mixture over 10% Pd/C in EtOH to afford 41% of lactam 12a and 10% of lactam 12b . The stereochemistry of the ring fusion was assigned by analogy to oxidative cyclization of 3 with other trapping reagents .…”