SQL query returns `ERROR: syntax error at or near "union"`

I am a beginner in SQL. What is the syntax issue with the query shown here?

I just needed the random rows to be present n number of times.

with recursive cte1 as 
(
    select 1 as idx, company_id, field_values 
    from transaction_detail 
    where company_id = 12345 
    limit 1

    union all 

    select idx + 1 as idx, company_id, field_values 
    from transaction_detail 
    where company_id = 12345 
    limit 1
    where idx < 6
)
select * 
from cte1;

Error is

ERROR: syntax error at or near "union"
LINE 3: union all

SQL state: 42601
Character: 145

Your CTE is not recursive. Mistakenly, you select from the table again instead of the CTE, which is what would create the recursion.

Then, a LIMIT clause refers to the whole query, but the query has two parts glued with UNION ALL. In order to make the first part a separate query with an own LIMIT clause, you need parantheses around it.

The corrected query:

with recursive cte1 as 
(
    (
    select 1 as idx, company_id, field_values 
    from transaction_detail 
    where company_id = 12345 
    limit 1
    )
    union all 

    select idx + 1 as idx, company_id, field_values 
    from cte1 
    where idx < 6
)
select * 
from cte1;

Demo: https://dbfiddle.uk/gfDNQ21m

An alternative is to select the one row in a separate (non-recursive) CTE first:

with recursive 
  one_row as
  (
    select *
    from transaction_detail 
    where company_id = 12345 
    fetch first row only
  ),
  cte1 as 
  (
    select 1 as idx, company_id, field_values 
    from one_row 

    union all 

    select idx + 1 as idx, company_id, field_values 
    from cte1 
    where idx < 6
  )
select * 
from cte1;

Demo: https://dbfiddle.uk/52PKsIky

(I've used the standard SQL fetch first row only here instead of LIMIT, but that's just personal preference, it makes no difference to the query execution.)