rings4 - FOUR-MEMBERED RING FORMATION 4 Membered Rings 1....

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
FOUR-MEMBERED RING FORMATION 129 4 Membered Rings 1. 2. oxatanes Cyclobutanes - [2+2] cycloadditions - photochemical cycloadditions (2 π s +2 π s ) Acc. Chem. Res. 1968 , 1 , 50; Synthesis 1970 , 287; Acc. Chem. Res. 1971 , 4 , 41; Organic Photochemistry 1981 , 5 , 123; Angew. Chem. Int. Ed. Engl. 1982 , 21 , 820; Acc. Chem. Res . 1982 , 15 , 135; Organic Photochemistry 1989 , 10 , 1 Organic Reactions 1993 , 44 , 297 - for synthetic purposes, cyclic α , β -unsaturated carbonyl are the most useful. E 1 E* 3 E* intersystem crossing - symmetry requirements O HOMO O LUMO h ν 2 π s + 2 π s ~ 340 nm * - enones with olefins O CH 2 CH 2 O O O O O + h ν + + (90%) JCSCC 1966 , 423 O O H + h ν + Caryophellene E.J. Corey JACS 1963 , 85 , 362 O H Base Hot Ground State? O h ν O H 2 C=CH 2 2 π s + 2 π a thermal cyclization O H H cis ring-fusion isomerization N CH 3 H O CH 3 N CH 3 H O CH 3 H 2 C=CH 2 h ν , CH 2 Cl 2 Ph CH 3 O HO CH 3 grandisol JACS 1986 , 108 , 306
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/11/2012 for the course CHEM 233 taught by Professor Staff during the Fall '10 term at Vanderbilt.

Page1 / 6

rings4 - FOUR-MEMBERED RING FORMATION 4 Membered Rings 1....

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online