Tandem with nitrogen transfer reactions

Because eluent molecules (e.g., water, methanol) are present in excess relative to the analytes in the sample, they are predommantly ionized and then act as a reagent gas that reacts secondarily to ionize analyte molecules (Figure 7-5, B). Because the products of these secondary reactions may contain clusters of solvent and analyte molecules, either a heated transfer tube or a countercurrent flow of a curtain gas, such as nitrogen, is used to decluster the ions. There is relatively little fragmentation, so much work with APCI has been for quantitative analysis or for tandem MS. As a well-proven interface, APCI sources are available from the major instrument manufacturers (see ESI section above). 

Inter- and intra-molecular [3 + 2] photocycloadditions of 1,3-dipolar species generated by elimination of nitrogen from tetrazoles (103) with alkenes (104) have been reported giving pyrazolines (105). Polycyclic azaheterocycles (108) (110) were also synthesized by [3 + 2] tandem photocycloaddition reactions. Intramolecular-proton-transfer mediated photocycloaddition of 3-hydroxyquinolones (111) with alkenes (113) to give [3 + 2] cycloadducts (114). ... 

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