compling mutiple sass files into multiple css in gruntfile.js not working

Question

I have my folder structure as below

-project_folder

• sass
  • vendors
  • modules
  • partials
    • sass1.scss
    • sass2.scss
• css
• index.html

I want to compile sass files without compass, using grunt to each seperate css files, (sass1.css , sass2.css)

I tried with the code

module.exports = function (grunt) {
  grunt.initConfig({

// SASS config
sass: {
    dist: {
     options: {
       style: 'nested',
       sourcemap: 'none',
       cache: false
     },
         files: [{
            expand: true,
            cwd: 'sass',
            src: ['*.scss'],
            dest: 'css/'
        }]
     }
    }
  });

But this isn't generating the css files. Please provide your solution.