Haloperidol synthesis - 1-chloro-4-(prop-1-en-2-yl)benzene with NH4Cl and formaldehyde

**However I have no idea how the first two steps work. Especially the first step makes me wonder how the amine and the aldehyde form the 1,3-oxazinane.** 


[![enter image description here](https://i.stack.imgur.com/Fjr9t.png)](https://i.stack.imgur.com/Fjr9t.png)


Suggestions:
Ammonia and formaldehyde form via condensation the imine. 
The imine and formaldehyde form the 1,3-oxazinane, however I looks kinda wrong to me. Moreover, if this is mechanism would be correct, why does the formaldehyde binding to prop-1-en and the imine don't?


[![enter image description here](https://i.stack.imgur.com/cBgbi.png)](https://i.stack.imgur.com/cBgbi.png)


Step 2 probably starts with protonating the oxygen and i think the 1,3-oxazinane cleavage follows after. However how does the methyl group bonds with the other methylene group?


[![enter image description here](https://i.stack.imgur.com/KQmlB.png)](https://i.stack.imgur.com/KQmlB.png)


