Transmission of polar substituent effects in the adamantane ring system as monitored by 19F NMR

✍ Scribed by William Adcock; Neil A. Trout

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 268 KB
• Volume: 36
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199803)36:3<181::aid-omr250>3.0.co;2-a

✦ Synopsis

An extensive series of (E)/(Z)-5-substituted(X)adamant-2-yl Ñuorides (2 and 3, respectively) and (E)/ (Z)-4-substituted(X)adamant-1-yl Ñuorides (4 and 5, respectively) were synthesized and characterized and their 19F chemical shifts measured in several solvents. Correlation of the 19F substituent chemical shifts (SCS) against polar Ðeld parameters together with comparisons against the 19F SCS of 4-substituted(X)bicyclo[2.2.2]oct-1-yl Ñuo-(p F ) rides (1) provide unequivocal evidence for the importance of electrostatic Ðeld and "through-three-bondÏ electron delocalization (double hyperconjugation) e †ects as long-range modes of transmission of polar e †ects in these saturated systems. The former e †ect is shown to be a function not only of spatial factors (angles and distance) but also the "sti †nessÏ of the CÈF p bond. The latter electronic mechanism is clearly the dominant factor regulating the 19F SCS of 2 and 4 but is switched "o †Ï in 3 and 5 as a result of speciÐc stereoelectronic requirements.