aws-cdk yarn synth -o /tmp/artifacts returning error ENOENT: no such file or directory, open '/tmp/artifacts/manifest.json'

I'm initiating an aws-cdk project with the following structure

src
└── cdk
    ├── config
    ├── index.ts
    ├── pipeline.ts
    └── stacks
node_modules
cdk.json
package.json

My package.json is as under

  "name": "my-project",
  "version": "1.0.0",
  "scripts": {
    "build:artifacts": "cdk synth -o tmp/artifacts",
    "watch": "tsc -w",
    "cdk": "./node_modules/.bin/cdk",
    "cdk-check": "yarn cdk doctor./node_modules/.bin/cdk",
    "typecheck": "tsc --noEmit",
    "lint": "eslint --cache --cache-location ./node-modules/.eslintcache --ext=.ts,.js ./src",
    "test": "yarn typecheck && yarn lint && yarn jest",
    "jest": "jest"
  },
  "devDependencies": {
    "@types/jest": "^27.5.2",
    "@types/node": "10.17.27",
    "@types/prettier": "2.6.0",
    "@typescript-eslint/eslint-plugin": "^5.33.0",
    "@typescript-eslint/parser": "^5.33.0",
    "aws-cdk": "2.37.1",
    "eslint": "^8.21.0",
    "jest": "^27.5.1",
    "ts-jest": "^27.1.4",
    "ts-node": "^10.9.1",
    "typescript": "~3.9.7"
  },
  "dependencies": {
    "aws-cdk-lib": "2.37.1",
    "constructs": "^10.0.0",
    "source-map-support": "^0.5.21"
  }
}

yarn lint and yarn typecheck runs ok

However, yarn build:artifacts returns following error

➜  src git:(feature/create-vpc) ✗ yarn build:artifacts
yarn run v1.22.18
warning package.json: No license field
$ cdk synth -o /tmp/artifacts

ENOENT: no such file or directory, open '/tmp/artifacts/manifest.json'
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

A delete node_module and yarn install everything again to no avail

Could someone please let me know why yarn build:artifacts is generating this error ??

BR

A couple of errors existed:

1. Firstable cdk.json app entry needed to point to index.ts "app": "npx ts-node --prefer-ts-exts src/cdk/index.ts"

2. index.ts needs to have app.synth() at the end as under

import 'source-map-support/register';
import * as cdk from 'aws-cdk-lib';
import { TestStack } from './pipeline';

const app = new cdk.App();
new TestStack(app, ‘TestStack', {
    env: { account: ‘123456789012, region: 'us-east-1' },
});
app.synth();

hope this helps