The boronate ester phase is attacked by the nucleophilic carbon atom of the leaving group, followed by a 1,2-migration to transform into a carbaboronate ester. This reaction is known as the Matteson reaction, which is essentially similar to the hydroboration-oxidation reaction. The research group of Guangbin Dong at the University of Chicago extended this reaction to aminoboronate esters, achieving the aza-Matteson reaction between N-B bonds. However, unlike the Matteson reaction, depending on the halogens on dihalomethane, they were able to control the formation of mono-insertion and double-insertion products.

<MultiModal>![[R]N(C1=CC=CC=C1)B2OC(C)(C)C(C)(C)O2 reacts with n-butyllithium and $CH_2XY$ at -78°C, followed by warming to room temperature and reaction with a Lewis acid.](/media/uploads/686fd954-bacc-4fd3-8246-f04ec1ef0af8.png)</MultiModal>

Which of the following statements are correct?
1. When using chlorobromomethane, a double-insertion reaction can occur.
2. When using dibromomethane, a double-insertion reaction can occur.
3. The reason double insertion can occur is that nitrogen's 1,2-migration can involve lone pair electrons, making the rate faster.
4. The reason the reaction stops at the double-insertion product is that the lone pair electrons of nitrogen in the double-insertion product can coordinate with the boronate ester, preventing further reaction.
硼酸酯相被连接离去基团的亲核性碳原子进攻，随后发生1,2-迁移转化为碳硼酸酯，此反应为Matteson 反应，其本质与硼氢化氧化反应类似。芝加哥大学董广彬课题组将这一反应拓展到氨基硼酸酯上，实现了N-B键之间的aza-Matteson 反应。然而，与Matteson反应不同，根据二卤代甲烷上卤素的不同，他们能够实现单插入和双插入产物的控制。

<MultiModal>![[R]N(C1=CC=CC=C1)B2OC(C)(C)C(C)(C)O2 在-78℃下与正丁基锂、$CH_2XY$反应后，升室温与Lewis酸反应。](/media/uploads/686fd954-bacc-4fd3-8246-f04ec1ef0af8.png)</MultiModal>

下面的说法中有哪些是正确的？
1. 当使用一氯一溴甲烷时，可以发生双插入反应
2. 当使用二溴甲烷时，可以发生双插入反应
3. 能发生双插入的原因是因为氮的1，2迁移可以有孤对电子参与，速率更快
4. 能停留在双插入产物的原因是因为双插入的产物中氮的孤对电子可以配位硼酸酯使得其无法继续反应
1.3.4.
2.3.4.
2.3.
2.4.
1.3.
1.4.
1.
2.
3.
4.
There is no correct statement.
1.3.4.
2.3.4.
2.3.
2.4.
1.3.
1.4.
1.
2.
3.
4.
没有正确的说法
In the lithium-halogen exchange reaction, **Br** is exchanged first. In the first insertion reaction, due to the better leaving ability of bromine compared to chlorine, when dibromomethane participates in the reaction, the tetracoordinated boron can undergo 1,2-nitrogen migration at low temperature to form a tricoordinated boron, which is further attacked by the second anion, resulting in a double insertion reaction. In contrast, chlorobromomethane requires room temperature for the chlorine atom to leave.  

Therefore, dibromomethane can undergo double insertion, while chlorobromomethane can only undergo single insertion.  

<Checkpoint>[Due to the better leaving ability of bromine compared to chlorine, when dibromomethane participates in the reaction, the tetracoordinated boron can undergo 1,2-nitrogen migration at low temperature.](1)</Checkpoint>  

<Checkpoint>[Therefore, dibromomethane can undergo double insertion, while chlorobromomethane can only undergo single insertion.](1)</Checkpoint>  

Thus, 2 is correct.  

Because the 1,2-migration of nitrogen can involve lone pair electrons, the reaction proceeds faster, so nitrogen migration reactions can occur rapidly at low temperatures. 3 is correct.  

<Checkpoint>[The 1,2-migration of N can involve lone pair electrons, resulting in a faster rate.](1)</Checkpoint>  

However, after completing one insertion, the reaction reverts to a carbon migration reaction, which requires room temperature to occur. 4 is incorrect.  

<Checkpoint>[After completing one insertion, the reaction reverts to a C migration reaction, which requires room temperature to occur.](1)</Checkpoint>  

In conclusion, choose C.
在锂卤交换反应中，**Br**会被首先交换。第一次插入反应中，由于溴的离去性比氯好，因此二溴甲烷参与反应时，四配位的硼可以在低温发生1，2氮迁移得到三配位硼，进一步被第二个负离子进攻，发生双插入反应，而一氯一溴甲烷必须在室温才能离去氯原子。
因此二溴甲烷可以发生双插入，一氯一溴甲烷只能发生单插入反应。

<Checkpoint>[由于溴的离去性比氯好，因此二溴甲烷参与反应时，四配位的硼可以在低温发生1，2氮迁移](1)</Checkpoint>

<Checkpoint>[因此二溴甲烷可以发生双插入，一氯一溴甲烷只能发生单插入反应。](1)</Checkpoint>

因此1错误，2是正确的。

因为N的1，2迁移可以有孤对电子参与，速率更快，所以迁移氮的反应可以在低温下快速发生。3正确

<Checkpoint>[N的1，2迁移可以有孤对电子参与，速率更快](1)</Checkpoint>

而当完成一次插入后，反应再次成为碳迁移反应，需要在室温下发生，4错误。

<Checkpoint>[完成一次插入后，反应再次成为C迁移反应，需要在室温下发生](1)</Checkpoint>

综上，选择C。