Structural studies of organoboron compounds. LVII. Synthesis and structure of bicyclic boron-nitrogen betaines. 1-Methyl-5-(3-nitrophenyl)-4,6,9-trioxa-1-azonia-5-boratabicyclo[3.3.1]nonane and 3,3,4-trimethyl-1-(3-nitrophenyl)-2,6,7-trioxa-3-azonia-1-boratabicyclo[2.2.2]octane

Abstract

The syntheses and structures of the bicyclic boron-nitrogen betaines l-methyl-5-(3-nitrophenyl)- 4,6, 7a, and 3,3, Introductionoxide 5 undergoing an intramolecular 0 + B coordination The condensation of bis(2-hydroxyethy1)amines 1 and arylboronic acids leads to 1,3-dioxa-6-aza-2-boracyclooctanes 2 that are known to undergo transannular N + B coordination to form the stable bicyclo[3.3.0]octane ring systems 3. The structure 3 for these materials has been confirmed by chemical and physical investigations ( I ) , including an X-ray crystallographic analysis of the N-unsubstituted derivative 3 (R = H, Ar = C6H,) (2). Employing the Noxides 4, obtained by reaction of 1 with hydrogen peroxide (3,4), the condensation with an arylboronic acid could result in both the eight-membered cyclic arylboronate 5 and the six-membered chelate 6.4 Both products (5 and 6) could subsequently cyclize to the bridged-ring compound 7 , the N-

Structural studies of organoboron compounds LVIII. 4-(1′-azoniabicyclo[2.2.2]-octanyl)-2,2-diphenyl-2-borata-1,3-dioxa-1,2,3,4-tetrahydronaphthalene

“…Moreover, a complex like 5 would represent a stabilized derivative of the labile zwitterionic '~revious paper in this series: ref. 19. '~uthor to whom correspondence may be addressed.…”