A process for assaying a compound of R-NH 2, comprising: forming a compound of Formula: by reacting a compound of Formula: with the compound of R-NH 2 in the presence of a cyanide ion; and detecting and measuring the fluorescence of the compound of Formula; wherein: X is N or CR a; R 1 and R 2 are R a; or R 1 and R 2 together with the carbon atoms they are attached to form a monocyclic or multicyclic fused aryl or heteroaryl ring, which is optionally substituted with one or more R a1; R 3 is hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of which is optionally substituted with one or more R b; R is a moiety, which is attached to a solid support directly or via a linker; each instance of R a is independently hydrogen, halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R a1 is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R b is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more halogen, alkyl, or alkoxy; and wherein the reaction between the compound of Formula and R-NH 2 occurs under a mildly basic condition having a pH of from 7.5 to 10. forming a compound of Formula: by reacting a compound of Formula: with the compound of R-NH 2 in the presence of a cyanide ion; and detecting and measuring the fluorescence of the compound of Formula; wherein: X is N or CR a; R 1 and R 2 are R a; or R 1 and R 2 together with the carbon atoms they are attached to form a monocyclic or multicyclic fused aryl or heteroaryl ring, which is optionally substituted with one or more R a1; R 3 is hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of which is optionally substituted with one or more R b; R is a moiety, which is attached to a solid support directly or via a linker; each instance of R a is independently hydrogen, halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R a1 is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R b is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more halogen, alkyl, or alkoxy; and wherein the reaction between the compound of Formula and R-NH 2 occurs under a mildly basic condition having a pH of from 7.5 to 10. X is N or CR a; R 1 and R 2 are R a; or R 1 and R 2 together with the carbon atoms they are attached to form a monocyclic or multicyclic fused aryl or heteroaryl ring, which is optionally substituted with one or more R a1; R 3 is hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of which is optionally substituted with one or more R b; R is a moiety, which is attached to a solid support directly or via a linker; each instance of R a is independently hydrogen, halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R a1 is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more R b; each instance of R b is independently halogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, hydroxyl, alkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, cyano, nitro, amino, amido, carboxyl, sulfonyl, sulfonamido, acyl, acyloxy, alkoxycarbonyl, or phosphate; each of which is optionally substituted with one or more halogen, alkyl, or alkoxy; and wherein the reaction between the compound of Formula and R-NH 2 occurs under a mildly basic condition having a pH of from 7.5 to 10.