What sequence of reactions would best accomplish the following conversion?
`CH_(3)-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-Hoverset(?)rarrCH_(3)overset(OH)overset("| ")"CH"CH_(2)CHO`

Options

A. `NaBH_(4)//H_(3)O^(+)`
B. `HOCH_(2)CH_(2)OH//H^(+), NaBH_(4), H^(+)//H_(2)O`
C. `KMnO_(4)//HO^(-)," heat"`
D. `LiAlH_(4)//H_(3)O^(+)`

Answer

To accomplish the conversion from the compound \( CH_3C(=O)CH_2C(=O)H \) (which contains a ketone and an aldehyde) to \( CH_3CH(OH)CH_2CHO \) (which contains an alcohol and retains the aldehyde), we can follow these steps:

### Step 1: Protect the Aldehyde Group
- Start with the compound \( CH_3C(=O)CH_2C(=O)H \).
- Treat it with ethylene glycol \( HOCH_2CH_2OH \) in the presence of an acid catalyst (H+). This will protect the aldehyde group, forming a cyclic acetal or a similar protective group.

### Step 2: Reduce the Ketone Group
- Next, treat the protected compound with sodium borohydride \( NaBH_4 \). This reagent selectively reduces the ketone group to a secondary alcohol while leaving the protected aldehyde intact.
- The reduction of the ketone group will yield \( CH_3C(OH)CH_2C(=O)H \).

### Step 3: Deprotect the Aldehyde Group
- Finally, remove the protecting group by treating the compound with acid and water (H+ and H2O). This step will regenerate the aldehyde group.
- The final product will be \( CH_3CH(OH)CH_2CHO \).

### Summary of the Sequence
1. Protect the aldehyde using ethylene glycol in acid.
2. Reduce the ketone using sodium borohydride.
3. Deprotect the aldehyde using acid and water.

### Final Answer
The correct sequence of reactions is:
1. Ethylene glycol (HOCH2CH2OH) + H+ (acid) → Protect the aldehyde.
2. \( NaBH_4 \) → Reduce the ketone to alcohol.
3. H+ + H2O → Deprotect the aldehyde.