[babilon87]

Hi
For the first time, I get a new project. In this project, I need to make Grignard reagent. The Alkyl halide is 2-bromo allyl alcohol. So I think it should be protected with protecting group. so I did with Acetate.
Then I tried to generate Grignard reagent. But the generation is not good. I cannot observe even the initiation of Grignard showing grey color.

So I search some references, then I found that most Grignard reagents don't contain hydroxyl group.
Luckily I could find a reference containing hydroxyl group.

Org. Lett., 2005, 7 (13), pp 2599–2602

But in this paper, they used iPrMgCl first as a base and then generation of Grignard.
And other papers also, although after Grignard reaction, their compounds are protected.

Why they didn't protect compounds first? Is there any reason?

T^T
Thank you

[sjb]

Hi
For the first time, I get a new project. In this project, I need to make Grignard reagent. The Alkyl halide is 2-bromo allyl alcohol. So I think it should be protected with protecting group. so I did with Acetate.
Then I tried to generate Grignard reagent. But the generation is not good. I cannot observe even the initiation of Grignard showing grey color.

So I search some references, then I found that most Grignard reagents don't contain hydroxyl group.
Luckily I could find a reference containing hydroxyl group.

Org. Lett., 2005, 7 (13), pp 2599–2602

But in this paper, they used iPrMgCl first as a base and then generation of Grignard.
And other papers also, although after Grignard reaction, their compounds are protected.

Why they didn't protect compounds first? Is there any reason?

T^T
Thank you

You can argue that forming the anion is "protecting" the alcohol, in some way. Sometimes it is not worth the effort to protect, react, deprotect (be it economic, time-related, or other principles)

[discodermolide]

Hi
For the first time, I get a new project. In this project, I need to make Grignard reagent. The Alkyl halide is 2-bromo allyl alcohol. So I think it should be protected with protecting group. so I did with Acetate.
Then I tried to generate Grignard reagent. But the generation is not good. I cannot observe even the initiation of Grignard showing grey color.

So I search some references, then I found that most Grignard reagents don't contain hydroxyl group.
Luckily I could find a reference containing hydroxyl group.

Org. Lett., 2005, 7 (13), pp 2599–2602

But in this paper, they used iPrMgCl first as a base and then generation of Grignard.
And other papers also, although after Grignard reaction, their compounds are protected.

Why they didn't protect compounds first? Is there any reason?

T^T
Thank you

1 Grignards react with esters (acetate is an ester).
2 Protect, if you have to with a silly group.
3 iPrMgCl deprotonates the OH to give the magnesium alcholate, which takes no further part in the reaction, allowing the Grignard to form on the other end.

I would protect the alcohol.

[babilon87]

Hi
For the first time, I get a new project. In this project, I need to make Grignard reagent. The Alkyl halide is 2-bromo allyl alcohol. So I think it should be protected with protecting group. so I did with Acetate.
Then I tried to generate Grignard reagent. But the generation is not good. I cannot observe even the initiation of Grignard showing grey color.

So I search some references, then I found that most Grignard reagents don't contain hydroxyl group.
Luckily I could find a reference containing hydroxyl group.

Org. Lett., 2005, 7 (13), pp 2599–2602

But in this paper, they used iPrMgCl first as a base and then generation of Grignard.
And other papers also, although after Grignard reaction, their compounds are protected.

Why they didn't protect compounds first? Is there any reason?

T^T
Thank you

You can argue that forming the anion is "protecting" the alcohol, in some way. Sometimes it is not worth the effort to protect, react, deprotect (be it economic, time-related, or other principles)

Thank you for your kind advice. I need to protect the alcohol, because the product of grignard reaction is intermediate to final compound. There are some steps affecting primary alcohol.
Thank you !

[babilon87]

Hi
For the first time, I get a new project. In this project, I need to make Grignard reagent. The Alkyl halide is 2-bromo allyl alcohol. So I think it should be protected with protecting group. so I did with Acetate.
Then I tried to generate Grignard reagent. But the generation is not good. I cannot observe even the initiation of Grignard showing grey color.

So I search some references, then I found that most Grignard reagents don't contain hydroxyl group.
Luckily I could find a reference containing hydroxyl group.

Org. Lett., 2005, 7 (13), pp 2599–2602

But in this paper, they used iPrMgCl first as a base and then generation of Grignard.
And other papers also, although after Grignard reaction, their compounds are protected.

Why they didn't protect compounds first? Is there any reason?

T^T
Thank you

1 Grignards react with esters (acetate is an ester).
2 Protect, if you have to with a silly group.
3 iPrMgCl deprotonates the OH to give the magnesium alcholate, which takes no further part in the reaction, allowing the Grignard to form on the other end.

I would protect the alcohol.

In the first case, you mean generated grignard reagent can undergo intramolecular reaction?

Now I am considering your third suggestion. Thank you for your attention ^^

[discodermolide]

No an intermolecular reaction