烷基鋰化合物和帶有鄰位導向基團 (Directed Metalation Group--DMG)的芳烴反應得到鄰位金屬中間體。好的鄰位導向基團有很強的配位或螯合效應，導致鄰位氫的酸性增強。
鄰位金屬中間體可以和各種親電試劑反應，得到的產物的DMG可以複原，轉化為其他基團，或直接除去。
一般情況下此類反應都是低溫，強堿性條件，幾乎完全的鄰位選擇性是此反應的特點。
反應機理
電子密度大的取代基與鋰的相互作用，使得相鄰的位置被選擇性鋰化。
DMG沒必要必須是惰性基團:
反應實例
To a stirred solution of 3-phenylsydnone (1) (0.25 g, 1.54 mmol) in dry THF (100 ml) at
-78℃ under an atmosphere of dry nitrogen gas was added N, N, N’,
N’-tetramethylethylenediamine (0.29 ml, 1.93 mmol) then n-butyllithium (2.31 ml, 3.47
mmol, 15 M in pentane) dropwise. After 0.5 h, the appropriate
2-chloro-N-methoxy-N-methylacetamide (1.93 mmol) was added to the golden yellow
solution and, after a additional 1h, the mixture was quenched with aqueous hydrochloric acid
(100ml, 10% v/v) then extracted with dichloromethane (3*100 ml). the combined organic
layers were dried (MgSO4) and the solvent removed in vacuo to afford the corresponding
o-acylated sydnone 4as an oil which was puriied by colum chromatography to afford colorless
crystals. Yield 86%.
【Tetrahedron Lett.; EN; 39; 12; 1998; 1509-1512】
