The invention discloses a 1,2-dihydroisoquinolin derivative and a preparation method thereof, relating to a midbody which can be used for synthesizing natural
alkaloid and a preparation method thereof. The 1,2-dihydro-isoquinolin derivative has a structure of formula (I). In the formula, R1 is meta-position or ortho-position substituted
electron donating or weak
electron-withdrawing aromatic group or H; R2 is methyl or ethyl; R3 is
hydrogen or
alkyl; and R4 is meta-position or ortho-position substituted aromatic group. The mol ratio of diazonium,
alcohol (or water),
imine,
rhodium acetate and silver trifloromethanesulfonate is 1.2:1.2:1:0.01:0.05. A
solvent, the
alcohol (or water), the
imine and a catalyst are used for preparing a
mixed solution. Then, the diazonium is evenly mixed with another
solvent to prepare diazonium solution which is then infused into the
mixed solution. The
solvent is removed by reduced pressure
distillation at a temperatre of 40-70 DEG C. Column
chromatographic separation is carried out to obtain the pure product of the 1,2-dihydro-isoquinolin derivative. When the 1,2-dihydro-isoquinolin undergoes reduction reaction, a
tetrahydroisoquinoline derivative with pharmaceutical activity can be generated. The 1,2-dihydroisoquinolin derivative is an important
structural unit of a great number of natural products and can be used as a midbody which can be used for synthesizing natural
alkaloid.