Scope Iodolactonization

both five- , six-membered rings formed in iodolactonization shown below, five-membered ring formed preferentially predicted baldwin s rules ring closure. according rules, 5-exo-tet ring closures favored while 6-endo-tet ring closures disfavored. regioselectivity of each iodolactonization can predicted , explained using baldwin s rules.

stereoselective iodolactonizations have been seen in literature , can useful in synthesizing large molecules such aforementioned vernopelin , vernomenin because lactone can formed while maintaining other stereocenters. ring closure can driven stereocenters adjacent carbon-carbon multiple bond shown below.

even in systems without existing stereocenters, bartlett , coworkers found stereoselectivity achievable. able synthesize cis , trans 5 membered lactones adjusting reactions conditions such temperature , reaction time. trans product formed under thermodynamic conditions (e.g. long reaction time) while cis product formed under kinetic conditions (e.g. relatively shorter reaction time).

^ kurth, m. j.; brown, e. g.; lewis, e. j.; mckew, j. c. (1988). regioselectivity in iodolactonization of 1,6-heptadien-4-carboxylic acid derivatives . tetrahedron letters. 29 (13): 1517. doi:10.1016/s0040-4039(00)80340-8. 
^ baldwin, jack e. (1976). rules ring closure . journal of chemical society, chemical communications (18): 734. doi:10.1039/c39760000734. issn 0022-4936. 
^ hirschmann, h.; hanson, k.r. (1977). reflection-concordant stereospecific numbering . tetrahedron. 33 (8): 891–897. doi:10.1016/0040-4020(77)80042-2. issn 0040-4020. 
^ bartlett, p. a.; myerson, j. (1978). stereoselective epoxidation of acyclic olefinic carboxylic acids via iodolactonization . journal of american chemical society. 100 (12): 3950. doi:10.1021/ja00480a061.