Range hood exterior vent close to window?
there are not many specific guidelines .  all there is in the obc is this:


  9.10.22. Fire Protection for Gas, Propane and Electric Cooktops
  
  9.10.22.1. Installation of Ranges
  
  (1) Reserved
  
  (2) Clearances for and protection around gas, propane and electric ranges shall be not less than those provided in Articles
  9.10.22.2. and 9.10.22.3.
  
  9.10.22.2. Vertical Clearances above Cooktops
  
  (1) Except as provided in Sentence (2), framing, finishes and cabinetry installed directly above the location of the cooktop
  shall be not less than 750 mm above the level of cooktop burners or elements.
  
  (2) The vertical clearance described in Sentence (1) for framing, finishes and cabinets located directly above the location
  of the cooktop is permitted to be reduced to 600 mm above the level of the elements or burners provided the framing, finishes
  and cabinets,
  
  (a) are noncombustible, or
  
  (b) are protected by,
  
  (i) asbestos millboard not less than 6 mm thick, covered with sheet metal not less than 0.33 mm thick, or
  
  (ii) a metal hood with a 125 mm projection beyond the framing, finishes and cabinets.
  
  9.10.22.3. Protection Around Cooktops
  
  (1) Except as provided in Sentences (2) and (3), combustible wall framing, finishes or cabinets within 450 mm of the area
  where the cooktop is to be located shall be protected above the level of the heating elements or burners by material providing fire
  resistance not less than that of a 9.5 mm thickness of gypsum board.
  
  (2) Countertop splash boards or back plates that extend above the level of the heating elements or burners need not be
  protected as described in Sentence (1).
  
  (3) Except for cabinetry described in Article 9.10.22.2., cabinetry located not less than 450 mm above the level of the
  heating elements or burners need not be protected as described in Sentence (1).


and


  9.32.3.12. Outdoor Intake and Exhaust Openings
  
  (1) Separate air intake and exhaust outlet openings, when located on the same wall or roof, shall be installed so as to avoid
  contamination of the ventilation air by the exhaust air.
  
  (2) Intake openings shall be located so as to avoid contamination of the ventilation air from other local sources such as
  automobile exhausts and exhaust from adjacent buildings.
  
  (3) The distance from the bottom of an air intake opening to finished ground level or to any nearer and lower permanent
  horizontal surface shall be not less than 450 mm or the depth of expected snow accumulation, whichever is greater.
  
  (4) The distance separating air intakes from building envelope penetrations that are potential sources of contaminants,
  such as gas vents or oil fill pipes, shall be not less than 900 mm.
  
  (5) Air intakes shall be clearly labelled as such for identification from locations outside the dwelling unit.
  
  (6) The distance from the bottom of an exhaust outlet to finished ground level or to any nearer and lower permanent
  horizontal surface shall be not less than 100 mm.
  
  (7) Where air intake and exhaust openings are in exposed locations, provision shall be made to protect them from the entry
  of precipitation by the use of louvres, weather cowls or other suitable protection.
  
  (8) Air intake openings shall incorporate screens or grilles to protect against the entry of animals and insects.
  
  (9) Except for exhaust outlets serving heat recovery ventilators, exhaust outlets shall incorporate backdraft dampers.
  
  (10) Except for clothes dryers, exhaust outlets shall be fitted with screens of mesh not larger than 15 mm, except where
  climatic conditions may require larger openings.
  
  (11) Where a screen or grille required by Sentences (8) and (10) has a screen mesh less than 6 mm, the screen or grille
  shall be removable for cleaning.
  
  (12) The gross area of the screens or grilles installed in intake and exhaust openings shall be three times that of the duct
  served.
  
  (13) Screens and grilles shall be of corrosion-resistant material.
  
  (14) The net free area of an air intake or exhaust outlet shall be equal to or greater than the cross-sectional area of the duct
  served.
  
  9.32.3.13. Installation
  
  (1) Installation of fans and heat recovery ventilators shall be in accordance with manufacturer’s instructions for
  minimizing noise and vibration transmission and achieving the required sound rating.
  
  (2) Where flow-regulating dampers are required, they shall be adjustable and accessible without requiring the removal of
  fans, motors, or insulating materials and without the need for specialized tools.
  
  (3) Ventilation equipment shall be accessible for inspection, maintenance, repair and cleaning.
  
  (4) Ventilation equipment installed in unheated spaces shall be installed so as to avoid condensation of moisture on fans
  and motors in accordance with the manufacturer’s instructions.


however, if you are looking for advice:


in a solid masonry wall, a penetration through the wall for a vent stack or discharge should not be within 300 mm of a window or door lintel (this way you avoid a collapse of the hole from a transferred overhead load.  
if you have masonry lintel (caternary arch type), i would be very wary of doing a penetration anywhere near the foot of the arch without an engineer looking at it.  masonry lintels can exhibit huge horizontal compressive forces on a solid wall a long way horizontally from the foot.  you usually have to sleeve the interior of the penetration hole with a thick steel pipe section to take the load.
if you can't go through the wall for whatever reason, just go up.  you can either vent 


a) directly up through the attic space, then through the roof (just remember to use insulated pipe and a proper roof stack, cap and waterproof boot
b) up into the attic space and come out through the eave with a soffit drop vent port (just make sure to use insulated pipe and a drop vent with a baffle valve).  

do not, under any circumstances use flexible metal duct.  its not legal and it makes for a huge cleaning nightmare over time with a kitchen exhaust.  only use rigid galvanized steel duct pipe


hope that helps