In recent years, various one-pot multi-step reactions have been developed to construct aromatic heterocycles. Benzofuran, an important oxygen-containing heterocycle, is a key pharmacophoric scaffold for many bioactive compounds. The following reaction can construct 2,3-dialkyl-5-hydroxybenzofuran.

<MultiModal>![The reaction is represented by SMILES as, the first step O=C(C=C1)C=CC1=O.CC(C(C(C)=O)CC2=CC=C(Br)C=C2)=O>>[*], with conditions $K_2CO_3$, $CHCl_3$, 25$\degree C$, the second step of the reaction is the generation of **B** from **A**, with conditions $K_2CO_3$, $MeOH$, 25$\degree C$, the third step of the reaction is [B]>>CC1=C(C2=CC(O)=CC=C2O1)CC3=CC=C(Br)C=C3, with conditions conc., $HCl$, 25$\degree C$](/media/uploads/759fdc38-11d5-43d3-a1ad-d60d81579ef5.png)</MultiModal>

Deduce the structures of intermediates **A** and **B**. Regarding **A** and **B**, the following statements are made:

1. **A** has three rings.

2. The generation of **A** involves a tricyclic intermediate.

3. **A** contains four oxygen atoms.

4. The generation of **B** from **A** involves an enolate intermediate.

5. The generation of the product from **B** involves a hemiketal intermediate.

6. The driving force of the entire reaction lies in aromatization.

Let a be the sum of the squares of the serial numbers of the correct statements, and b be the square of the sum of the incorrect statements. Find a/b, rounded to three significant figures.
近年来，开发了多种一锅法多步反应构建芳香杂环的方法。苯并呋喃是一种重要的含氧杂环，是多种生物活性化合物的关键药效学框架。以下反应可以构筑2,3-二烷基-5-羟基苯并呋喃。

<MultiModal>![以SMILES表示反应为，第一步O=C(C=C1)C=CC1=O.CC(C(C(C)=O)CC2=CC=C(Br)C=C2)=O>>[*]，条件为$K_2CO_3$, $CHCl_3$, 25$\degree C$，第二步反应为由**A**生成**B**，条件为$K_2CO_3$, $MeOH$, 25$\degree C$，第三步反应为[B]>>CC1=C(C2=CC(O)=CC=C2O1)CC3=CC=C(Br)C=C3，条件为conc., $HCl$, 25$\degree C$](/media/uploads/759fdc38-11d5-43d3-a1ad-d60d81579ef5.png)</MultiModal>

推断中间产物**A**和**B**的结构，关于**A**,**B**有以下说法

1.**A**有三个环

2.生成**A**的过程中经历了三环中间体

3.**A**含四个氧原子

4.**A**生成**B**的过程中经历烯醇负离子中间体

5.**B**生成产物的过程中经历半缩酮中间体

6.整个反应的驱动力在于芳构化

设正确的说法序号的平方和为a，错误的说法的和的平方为b，求a/b，保留三位有效数字
All other options are incorrect
0.285
0.380
0.490
0.313
0.953
0.194
0.610
其他选项均不正确
0.285
0.380
0.490
0.313
0.953
0.194
0.610
First, in chloroform, the common α-hydrogen of the diketone is removed by a base, forming an enolate anion. The carbon end attacks the β-position carbon of the carbonyl group on the benzoquinone, forming an enolate anion on the benzoquinone, followed by rearomatization to form a hydroquinone anion structure. Subsequently, the phenoxide anion attacks the carbonyl carbon in the β-diketone, forming a five-membered ring and a hemiketal anion structure, followed by ring-opening, forming an enolate anion, and **A** is obtained after workup.

The intermediates for the formation of **A** are shown below.

<MultiModal>![Intermediates for the formation of **A**. The first intermediate is represented by SMILES as CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2C=C(C=CC2=O)[O-]; The second intermediate is represented by SMILES as CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2=CC(=CC=C2[O-])O; The third intermediate is represented by SMILES as CC(=O)C1(CC2=CC=C(C=C2)Br)C3=CC(=CC=C3OC1(C)[O-])O; The fourth intermediate is represented by SMILES as CC([C-](C1=C(OC(C)=O)C=CC(O)=C1)CC2=CC=C(Br)C=C2)=O.](/media/uploads/2f0995f7-9fae-43e4-a6b7-78a7b1d46f2d.png)</MultiModal>

<Checkpoint>[The first intermediate for the formation of **A** is represented by SMILES as CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2C=C(C=CC2=O)[O-]](1)</Checkpoint>

<Checkpoint>[<Checkpoint>[The second intermediate for the formation of **A** is represented by SMILES as CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2=CC(=CC=C2[O-])O](1)</Checkpoint>

<Checkpoint>[The third intermediate for the formation of **A** is represented by SMILES as CC(=O)C1(CC2=CC=C(C=C2)Br)C3=CC(=CC=C3OC1(C)[O-])O](1)</Checkpoint>

<Checkpoint>[The fourth intermediate for the formation of **A** is represented by SMILES as CC([C-](C1=C(OC(C)=O)C=CC(O)=C1)CC2=CC=C(Br)C=C2)=O](1)</Checkpoint>

In protic solvents, **A** loses an acetyl group to form a phenoxide anion, and then the phenoxide anion attacks the ketone carbon to generate a hemiketal anion, and hemiketal **B** is obtained after workup.

The structures of **A** and **B** are represented by SMILES as CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O and CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1, respectively, as shown in the figure below.

<MultiModal>![The structures of **A** and **B** are represented by SMILES as CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O and CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](/media/uploads/6f1eea9e-4c8b-41a8-8cb2-290aae6bc280.png)</MultiModal>

<Checkpoint>[The structure of **A** is represented by SMILES as CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O](2)</Checkpoint>

<Checkpoint>[The structure of **B** is represented by SMILES as CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](2)</Checkpoint>

The transformation from **A** to **B** involves two intermediates as shown in the figure below.

<MultiModal>![Two intermediates for the formation of **B** from **A**. The first intermediate is represented by SMILES as CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)[O-])=O; The second intermediate is represented by SMILES as CC1([O-])C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1.](/media/uploads/8b97c0b5-f681-4d7c-ad05-8096023b9427.png)</MultiModal>

<Checkpoint>[The first intermediate for the formation of **B** from **A** is represented by SMILES as CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)[O-])=O](1)</Checkpoint>

<Checkpoint>[The second intermediate for the formation of **B** from **A** is represented by SMILES as CC1([O-])C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](1)</Checkpoint>

Subsequently, **B** undergoes dehydration under concentrated, acidified conditions to form a benzofuran product.

<Checkpoint>[Dehydration of **B** to generate the product](1)</Checkpoint>

Now, determine whether each statement is correct or not. **A** has two rings, statement 1 is incorrect. The third intermediate for the formation of A has 3 rings, statement 2 is correct. **A** has 4 oxygen atoms, statement 3 is correct. The formation of **B** from **A** does not involve an enolate anion, statement 4 is incorrect. The formation of the product from **B** only involves an oxonium ion intermediate, statement 5 is incorrect. A benzene ring is formed during the formation of **A**, and a furan ring is formed during the formation of **B**. Aromatization is an important driving force for the reaction, statement 6 is correct.

The sum of the squares of the correct statement numbers is a, and the sum of the squares of the incorrect statement numbers is b. $a=4+9+36=49$, $b=(1+4+5)^2=100$, $a/b=0.490$, choose D.
首先，在三氯甲烷中，二酮共同的α氢被碱去除，形成烯醇负离子，碳端进攻苯醌上羰基的β位碳，在苯醌上形成烯醇负离子，随后重新芳构化形成对苯二酚负离子结构，随后酚氧负离子进攻β-二酮中的羰基碳，形成五元环和半缩酮负离子结构，随后开环，形成烯醇负离子，后处理后得到**A**。

形成**A**的中间体见下图

<MultiModal>![生成**A**的中间体。第一个中间体以SMILES表示为CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2C=C(C=CC2=O)[O-]；第二个中间体以SMILES表示为CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2=CC(=CC=C2[O-])O；第三个中间体以SMILES表示为CC(=O)C1(CC2=CC=C(C=C2)Br)C3=CC(=CC=C3OC1(C)[O-])O；第四个中间体以SMILES表示为CC([C-](C1=C(OC(C)=O)C=CC(O)=C1)CC2=CC=C(Br)C=C2)=O。](/media/uploads/2f0995f7-9fae-43e4-a6b7-78a7b1d46f2d.png)</MultiModal>

<Checkpoint>[生成**A**的第一个中间体以SMILES表示为CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2C=C(C=CC2=O)[O-]](1)</Checkpoint>

<Checkpoint>[<Checkpoint>[生成**A**的第二个中间体以SMILES表示为CC(=O)C(CC1=CC=C(C=C1)Br)(C(=O)C)C2=CC(=CC=C2[O-])O](1)</Checkpoint>

<Checkpoint>[生成**A**的第三个中间体以SMILES表示为CC(=O)C1(CC2=CC=C(C=C2)Br)C3=CC(=CC=C3OC1(C)[O-])O](1)</Checkpoint>

<Checkpoint>[生成**A**的第四个中间体以SMILES表示为CC([C-](C1=C(OC(C)=O)C=CC(O)=C1)CC2=CC=C(Br)C=C2)=O](1)</Checkpoint>

**A**在质子溶剂中，脱去乙酰基形成酚负离子后，酚负离子进攻酮碳生成半缩酮负离子，后处理得到半缩酮**B**。

**A**和**B**的结构以SMILES表示分别为CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O，CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1，结构如下图所示

<MultiModal>![**A**和**B**的结构以SMILES表示分别为CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O，CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](/media/uploads/6f1eea9e-4c8b-41a8-8cb2-290aae6bc280.png)</MultiModal>

<Checkpoint>[**A**的结构以SMILES表示为CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)OC(C)=O)=O](2)</Checkpoint>

<Checkpoint>[**B**的结构以SMILES表示为CC1(O)C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](2)</Checkpoint>

**A**到**B**经历两个中间体如下图所示

<MultiModal>![由**A**生成**B**的两个中间体。第一个中间体以SMILES表示为CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)[O-])=O；第二个中间体以SMILES表示为CC1([O-])C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1。](/media/uploads/8b97c0b5-f681-4d7c-ad05-8096023b9427.png)</MultiModal>

<Checkpoint>[**A**生成**B**的第一个中间体以SMILES表示为CC(C(CC1=CC=C(C=C1)Br)C2=C(C=CC(O)=C2)[O-])=O](1)</Checkpoint>

<Checkpoint>[**A**生成**B**的第二个中间体以SMILES表示为CC1([O-])C(CC2=CC=C(C=C2)Br)C3=C(C=CC(O)=C3)O1](1)</Checkpoint>

随后**B**在浓缩，酸化的条件下脱水形成苯并呋喃产物。

<Checkpoint>[**B**脱水生成产物](1)</Checkpoint>

现判断各说法正确与否，**A**有两个环，说法1错误，生成A的第三个中间体有3个环，说法2正确，**A**有4个氧原子，说法3正确，**A**生成**B**不经历烯醇负离子，说法4错误，**B**生成产物只经历氧鎓正离子中间体，说法5错误，生成**A**时生成了苯环，生成**B**时生成了呋喃环，芳构化是反应进行的重要动力，说法6正确。

正确的说法序号的平方和为a，错误的说法的和的平方为b。$a=4+9+36=49$，$b=(1+4+5)^2=100$，$a/b=0.490$，选择D。