automatically set alarm clock on iPhone if calendar event
There is a app on iTunes that might do just what you want.

Calarm: Calendar Alarm Clock
By squishLogic

For $1 it is worth trying.

This app will automatically wake you up every day before your first calendar event and alert you about events during the day.

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Alarms for all calendar events, including all-day and birthdays
• Ability to cancel specific alarms
• Ability to mute specific alarms
• Ability to change alert time for specific alarms
• Quick alarms - great for naps
• Send Quick alarms as a reminder to a friend
• No need to customize events
• No need to open the calendar app
• Select which calendars make alarms
• Adjustable wake up time
• Separate time interval for daytime events
• Reads calendar app, so no internet connection is needed
• Snooze any event
• 5-15 minute adjustable snooze interval
• Shows event on the lock screen with time until event and location
• Confirmation tab listing all scheduled alarms for the week
• View that shows events for a given day
• Control alarms for busy or free events
• 20 different alarm sounds
• Set up behaviors to better customize to your needs
• 12/24 hour clock
• Control event behavior from notes
• See alarm location, time, end time, and calendar
• Alarms can be defaulted to on, off, or muted
• Alarms can be set to sound until you dismiss them