Control ring

Synthesis. The synthesis of poly(dichlotophosphazene) [25034-79-17, (N=PCl2) (4), the patent polymer to over 300 macromolecules of types (1) and (2), is carried out via controlled, ring-opening polymerization of the corresponding cycHc trimer, (N=PCl2)3 [940-71 -6]. 

Stridsberg, K. M., Ryner, M. and Albertsson, A.-C. Controlled Ring-Opening Polymerization Polymers with Designed Macromoleculars Architecture. Vol. 157, pp. 27-51. 

The structural factors controlling ring-closure reactions behave similarly in many significant chemical reactions or transformations, proceeding... 

Stridsberg KM, Ryner M, Albertsson A-C (2002) Controlled ring-opening polymerization polymers with designed macromolecular architecture. Adv Polym Sci 157 42-139... 

Coulembier O, Degee Ph, Hedrick JL, Dubois Ph (2006) From controlled ring-opening polymerization to biodegradable aliphatic polyester especially poly(P-malic acid) derivatives. Prog Polym Sci 31 723-747... 

Martin E, Dubois P, Jerome R (2000) Controlled ring-opening polymerization of e-caprolactone promoted by in situ formed yttrium alkoxides. Macromolecules 33 1530-1535... 

Save M, Schappacher M, Soum A (2002) Controlled ring-opening polymerization of lactones and lactides initiated by lanthanum isopropoxide, 1 general aspects and kinetics. Macromol Chem Phys 203 889-899... 

Oshimura M, Takasu A (2010) Controlled ring-opening polymerization of E-caprolactone catalyzed by rare-earth perfluoroalkanesulfonates and perfluoroalkanesulfonimides. Macromolecules 43 2283-2290... 

A very powerful inhibitor, which is a bicyclic analogue of (33), is 6-acetamido-6-deoxycastanospermine (49), a compound synthesized from castanospermine and tested by Liu and co-workers [99]. This compound, amongst many other 6-modified castanospermine derivatives, was also prepared by the Furneaux team [100]. Furthermore, by controlled ring-contraction of suitably substituted castanospermine derivatives, these workers gained access to 8-acetamido-8-deoxyaustraline (50), a byciclic analogue of l-acetamido-l,2,5-trideoxy-2,5-imino-D-mannitol (44). This ring contraction reaction, which proceeds via a tricyclic aziridinium intermediate, is based on the same principle as the approach by Peter et al. to compound (45) [95]. 

Figure 13.35 Redox controlled ring rotation in solution for catenane 404+, which contains the symmetric electron acceptor cyclophane 124+ and a nonsymmetric electron donor ring.

The theory of branching processes and kineticaHy controlled ring-chain equilibria. IUPAC Symposium on Macromolecular Chemistry, Prague 1965. Preprint P 513. 

The cyclopropane ring can also be cleaved by a retro-Michael reaction. By appropriate positioning of the carbonyl groups by means of an intramolecular cyclopropanation, controlled ring opening to spiro systems (62),84 bicyclo[3.2.1]octanes (63)82 or bicyclo[2.2.2]octanes (64),82 has been achieved (equations 28-30). 

Control ring Essential for the correct operation of the valve as it determines the overpressure and blowdown values. It is usually screwed on the nozzle and blocked by a pin. 

---