Agapkin,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.leftmenu.block{
margin-top:15px;
width:100px;
height:100px;
background:green;
display:block;
position: relative;
}
.lalala {
display: none;
}
.leftmenu.block.open-block-leftmenu .lalala {
position: absolute;
display: block;
top: 50px;
left: 100%;
width: 100px;
height: 100px;
background: red;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
var leftmenu = $(".leftmenu");
leftmenu.on("click",function(event) {
if($(event.target).is(".lalala")) return;
leftmenu.not($(this).toggleClass("open-block-leftmenu"))
.removeClass("open-block-leftmenu")
})
});
</script>
</head>
<body>
<div class="leftmenu block">
<div class="lalala">
</div>
</div>
<div class="leftmenu block">
<div class="lalala">
</div>
</div>
<div class="leftmenu block">
<div class="lalala">
</div>
</div>
</body>
</html>