d <- data.frame(
  x1 = c(1, 2, 3, 4), 
  x2 = c(0, 0, 1, 1),
  y = c(3, 3, 4, -5), 
  wt = c(1, 2, 1, 1))

outcome_name <- "y"
explanatory_vars <- c("x1", "x2")  
name_for_weight_column <- "wt"

formula_str <- paste(outcome_name, "~", paste(explanatory_vars, collapse = " + "))
#[1] "y ~ x1 + x2"

eval(bquote(lm(formula_str, data = d, weights = .(as.name(name_for_weight_column)))))