E2 eliminations occur when the leaving group and the proton are in the anti-periplanar conformation not syn-periplanar. This is beyond a merely a preference as leads to E2 reactions being stereoselective. However, when it comes to vinyl bromides for example (involving a double bond) the reaction can occur in the Z- and E- isomers (i.e both syn-periplanar and anti-periplanar). How can this be the case? 


Question: Why would analysts recommend buying companies with negative net income?
Answer: The biotechnology sector as a whole is a popular buy recommendation among some analysts these days for a few reasons. 


Some analysts feel that the high costs in R&amp;D, even without much profit, are a positive sign for growth because it means a company is working towards finding the next "blockbuster drug" or the next class of such drugs. There haven't been many new classes of blockbuster drugs since the development of SSRI's and statins, and many of the new drugs that have been developed have been tweaks to existing classes of drugs. Some analysts feel that "it's about time" for a new class of blockbuster drugs to hit the market. A new blockbuster drug means significant profits for the company that develops it; a new class of blockbuster drugs means significant profits for the whole industry. 
Since about 2009, the Food and Drug Administration has been more lenient in its approval of new drugs. This wave of new approvals has reduced R&amp;D costs for companies because they don't need to go back to the lab or earlier phases of clinical trials and continually tweak their drugs in order to gain approval. This has also made some analysts optimistic.
Genetic engineering is considered an up-and-coming field with potentially significant applications to the pharmaceutical industry. Advances in this field may increase profits for the pharm industry, but since biotech companies are often the ones producing the engineering equipment, research, etc. such advances could be a major source of revenue for the entire biotech industry. 
In the US and in the developed world as a whole, the elderly population is growing, and since people consume more medicine as they grow older, this could lead to higher profits for companies involved in the production of pharmaceuticals (which includes biotech companies, of course) in the long run. 
In the US, the passage of the Patient Protection and Affordable Care Act expanded insurance coverage, which gives more people the means to afford pharmaceuticals. Also, in general, people consume more healthcare services when they have insurance (this is called moral hazard), so some analysts expect that the expansion of insurance coverage will only lead to more profits for the pharmaceutical industry and biotechnology firms in general.
The global food crisis. As the climate changes, companies like Monsanto, which use various forms of genetic engineering to produce crop strains that can survive in increasingly hostile environments, look more and more appealing to places that need crops designed to grow in such environments. Any methods that could increase yields look increasingly popular, and biotechnology companies often market such methods. (As a side note, I know Monsanto is a contentious example, and there are a lot of misconceptions about "genetically modified food" and the genetic engineering methods they do, so I won't get into a debate about that). 
In general, technology is a popular subject right now. I've read analyst reports (from analysts that clearly don't follow the biotech sector) that base their forecasts for the biotech sector on the activities of companies like Dell, Zynga, HP, LinkedIn, Facebook, etc. Clearly, it's problematic when an analyst sees the word "technology" and automatically assumes that the biotech sector is responsive to the same factors as social media firms, hardware manufacturers, etc. This isn't to say that the biotech sector is completely isolated from this, but when I read a report that talks about Facebook's IPO being bad news for companies like Gilead Sciences without mentioning upcoming FDA decisions about Gilead's products or any biotech-specific factors, I'm not convinced the analyst has performed due diligence. 


I keep using the phrase "some analysts" because I want to stress that the opinions stated above aren't universal. Although they're popular, not everyone is so optimistic. Also, I don't want you to see these reasons and think that I'm making a buy recommendation, because I'm not. I'm not making a recommendation one way or another. 

I'm happy to clarify my answer too; I follow the biotechnology sector extensively. If you want to get a rough feel for the daily movements of the sector as a whole, a good place to start is IBB, the iShares Nasdaq Biotechnology Index Fund. The four largest holdings are Regeneron, Gilead Sciences, Amgen, and Celgene, which are all big players in the industry (obviously). These are a little different from the big name pharma companies like Pfizer, Merck, Novartis, etc. but they're still considered pharma companies.

It's also worthwhile to follow the FDA press announcements. By the time the news is published there, it's probably already leaked or known to people in the industry (the biotech/pharm sectors are rife with accusations of insider trading), so you might not find trading opportunities, but it's important to get familiar with the information the releases contain if you want to know more about the industry. Volatility trades are always popular trades around FDA drug approvals.