I don't have anything like that in my output:
list(a = 1,b = 2,c = 3)
#> $a
#> [1] 1
#>
#> $b
#> [1] 2
#>
#> $c
#> [1] 3
Created on 2018-07-16 by the reprex package (v0.2.0).
In general, backticks are needed when name is not syntactically valid. For example:
list(`Not a valid name` = 1,b = 2,c = 3)
#> $`Not a valid name`
#> [1] 1
#>
#> $b
#> [1] 2
#>
#> $c
#> [1] 3
Created on 2018-07-16 by the reprex package (v0.2.0).
Could it be that you are typing a in your input from a different language?