Btirgi-Dunitz trajectory

The nucleophile will approach along the Btirgi-Dunitz trajectory, approximately 100-110° from the carbonyl oxygen (Figures 4.6 and 4.7). 

First, as shown in Figure 9.7, it is widely recognized that the favored trajectory (the Btirgi-Dunitz trajectory ) for addition of an electron rich species (X ) to the carbonyl (C=0) proceeds by a path that requires minimum subsequent distortion to produce the appropriate tetrahedral angle (or nearly so). In particular, this process, which is of paramount importance in ring closure reactions, introduces the necessity of asking whether the re or si face of an asymmetrically substituted carbonyl group (C=0) is attacked. 

Sir Robert Robinson played an early central role in the development of the electronic theoiy of organic chemistry (5S). For example, he was the first to use the now commonplace curly arrow to imply the reorganization of electron density during the course of a chemical reaction (59). The constract of stereoelectronic control (which, in its most literal sense, explains all chemical reactions) underpins many concepts now in the lexicon of mechanistic and synthetic organic chemistry. These include the Hammond postulate, the Curtin-Hammett Principle, the Markovnikov rule (for additions to alkenes), the Thorpe-lngold effect (on rates of cyclization), the Btirgi-Dunitz approach trajectory, Cram/Comforth/Felkin-Ahn controlled additions (to chiral ketones... 

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