catalog.start_execution SYNCHRONIZED in Transaction

Hi, I am trying to execute a SSIS Package from a stored procedure within a transaction. I also want the execution to be in Synchronized mode. This is an example of my stored procedure code:

begin try
begin transaction

	/*
	inserts, updates
	*/

	declare @execution_id bigint
	EXEC [SSISDB].[catalog].[create_execution]	@package_name=N'My Package.dtsx',
												@execution_id=@execution_id OUTPUT,
												@folder_name=N'MyFolder',
												@project_name=N'MyProject',
												@use32bitruntime=False,
												@reference_id=Null
	EXEC [SSISDB].[catalog].[set_execution_parameter_value] @execution_id,
															@object_type=50,
															@parameter_name=N'LOGGING_LEVEL',
															@parameter_value= 1
	EXEC [SSISDB].[catalog].[set_execution_parameter_value] @execution_id,
															@object_type=50,
															@parameter_name=N'SYNCHRONIZED',
															@parameter_value= 1
	EXEC [SSISDB].[catalog].[start_execution] @execution_id;

	/*
	throw error if execution status is not = 7 ("Success")
	*/

commit transaction
end try
begin catch
	if @@Trancount > 0
		rollback transaction;
end catch

The problem is that the package reaches a timeout and gets a status = 5 ("Pending").

If I remove the Synchronized setting, it works. If I remove the transaction, it works. But a combination of both will not work. Can anyone think of a simple workaround for this?

Thank you,

Filip