[{"_id":"1234","type":"automatic","subtypes":[{"_id":"dfgd","name":"test subtype","subjetRequired":true,},{"_id":"dfgd","name":"test subtype2","subjetRequired":false,}],"anotherField":"some value"}]

db.collection.update({"subtypes.subjetRequired":{$exists:true}},[{$set:{subtypes:{$map:{input:"$subtypes",in:{$mergeObjects:["$$this",{subjectRequired:"$$this.subjetRequired",}]}}}}},{$unset:"subtypes.subjetRequired"}],{"multi":true,"upsert":false})