endo,endo-5,9-Dibromo-cis-transoid-cis-13-oxatricyclo[8.2.1.02,6]tridecane

Abstract

1961considers the standard deviations of the bond lengths. We have therefore recalculated the bond lengths, angles and e.s.d.'s for the room-temperature structure.) The advantage in determining the structure at 120 K is reflected by significantly smaller standard deviations in the bond lengths. A similar observation has been made for p-chloranil where the low-temperature crystal structure (van Weperen & Visser, 1972) agrees better with the electron diffraction results than it does with the room-temperature structure (Chu et aL, 1962). In

(E)-exo,endo-2,5,10-Tribromo-exo-6-methoxy-13-oxa-cis-bicyclo[7.3.1]tridec-4-ene

“…The bond distances and angles are normal. The Br(1) double bond causes shortening of the Br--C bond Br(2) distance from the normal average value of Br (3) O (1) 1.968 (9)A (Br---Cs~) found in this type of corn-0(2) pound (Rissanen et al, 1987;Haufe, Faure & c(1) Loiseleur, 1987;Rissanen & Haufe, 1988; this work) c(2) C(3) to 1.909 (7)A (Br--Cs:). Also the conformation of c(4) the ten-membered ring is changed from slightly to c(5) heavily distorted boat-chair-boat conformation c(6) C(7) (Rissanen & Haufe, 1988).…”

“…The tricyclic compound is formed by transannular 7r-cyclization and subsequent transannular O-heterocyclization. In the reaction of (E,Z,Z)-cyclododeca-l,5,9-triene under the endo,endo-5,9-dibromo-cistransoid-cis-13-oxatricyclo[8.2.1.02'6]tridecane (15%) was formed by the same mechanism (Rissanen, Valkonen & Haufe, 1987); now an oxabicyclic compound (11%), one 7r-cyclization product and minor amounts of simple addition products have been isolated as well. To establish the composition, configuration and conformation of this unknown oxabicyclic product, we determined its crystal and molecular structure.…”

endo,endo,exo-2,6,10-Tribromo-exo-5-methoxy-13-oxa-trans-bicyclo[7.3.1]tridecane

“…Two types of transannular cyclizations have been observed in the methoxybromination of cycloalkadienes and cycloalkatrienes with medium-and large-sized rings. Transannular n-cyclizations with formation of bicyclo[n.4.0]alkanes have been found for nine-, ten-and eleven-membered cycloalka-l,5-dienes (Haufe & Mfihlst~idt, 1979), whereas under similar conditions, transannular O-heterocyclizations with formation of oxabicyclic compounds have been found for eight-, twelve-and thirteen-membered 1,5-dienes and 1,5,9-trienes (Graefe, Haufe & M~ihlst~idt, 1976;Haufe, 1984;Haufe & M/ihlst~idt, 1984;Rissanen, Valkonen & Haufe, 1987). The reaction pathway is determined by the ring size, the configuration of the double bonds and the conformation of the unsaturated carbocycle.…”