No, it is not directly possible to obtain OAuth2 tokens for Gmail accounts using Azure as the authentication platform.
Azure Active Directory (Azure AD) and Google OAuth2 are separate identity and authentication systems. When working with Gmail, OAuth tokens must be obtained via Google's authentication system.
Depending on your scenario maybe you could implement a Single Sign-On (SSO) solution. Google supports SSO through SAML or OpenID Connect (OIDC) with Azure AD as an Identity Provider (IdP). This might be more complex, than implementing Gmail 2.0 OAuth access.