(Adds Holcim, Energia de Bogota, EI Towers, Yoox, Baker Hughes, RadioShack; updates Dow Chemical )
March 27 (Reuters) - The following bids, mergers, acquisitions and disposals were reported by 2000 GMT on Friday:
** Dow Chemical Co will separate a portion of its century-old chlorine business and sell it to Olin Corp in a tax-efficient deal worth $5 billion as part of efforts to shed low-margin assets.
** U.S. energy firm Chevron is seeking to sell its entire stake in Caltex Australia Ltd for about A$4.6 billion ($3.58 billion), exiting Australia's biggest refiner after nearly 40 years as falling oil prices and high costs hurt margins.
** A lender to bankrupt RadioShack Corp told a U.S. judge on Friday it was prepared to present a new offer that was a "significant improvement" over a rival proposal that was selected as a winning bidder at an auction this week.
** Several investor groups are readying bids for German motorway service station group Tank & Rast, in a deal worth up to 3.5 billion euros ($3.8 billion), sources familiar with the transaction said.
A consortium of Allianz, Munich Re MUVGn.DE (MEAG), sovereign wealth fund Abu Dhabi Investment Authority (ADIA) and Borealis, part of pension fund OMERS, aims to hand in an offer by a mid- to end-April deadline, the people said.
** Builders FirstSource Inc, a U.S. supplier of residential building products, is in discussions to acquire peer ProBuild Holdings Inc for about $1.5 billion, including debt, three people familiar with the matter said on Thursday.
** Amazon.com is in talks to buy online luxury retailer Net-a-porter in what could be the biggest acquisition yet for the e-commerce giant, but the negotiations are in early stages and could fall apart, Forbes reported, citing a person familiar with the matter.
** A leading shareholder in Swiss cement group Holcim wants to know who will lead an enlarged group to be formed in a merger with France's Lafarge before it decides whether to back the deal.
** Asset manager BlackRock Inc and U.S. private equity firm First Reserve have taken a joint stake worth around $900 million in the second phase of Mexico pipeline project Los Ramones, state-controlled oil company Pemex said on Twitter on Thursday.
** Italian broadcast tower operator EI Towers, controlled by former Prime Minister Silvio Berlusconi's Mediaset group, won backing from shareholders on Friday for its bid to acquire state-owned rival Rai Way.
** Colombia's Energia de Bogota SA (EEB) has bought a 51 percent stake in four power transmission concessions in Brazil for around $170 million, a transaction that marks the company's entry into the region's largest economy, the company said on Friday.
** Austrian property group Immofinanz is seeking to lower the threshold for a mandatory takeover offer to 15 percent of its shares, which could force the hand of rivals such as CA Immo attempting to gradually build up a stake in the company.
** Shareholders on Friday voted to approve the mergers of rival oilfield services firms Baker Hughes Inc and Halliburton, bringing the proposed deal that still lacks regulatory approvals a step closer to finalization.
** Online fashion retailers Yoox and Richemont's Net-a-Porter are trying to resuscitate merger talks that took place more than a year ago to better fight cut-throat competition, industry sources told Reuters.
** Air Berlin expects to have made some decisions on which non-core businesses to divest by around mid-year, as part of turnaround measures being put in place by its new chief executive.
** Hedge fund Elliott Management disclosed a 7.5 percent stake in Swedish surveillance camera maker Axis AB, potentially raising pressure on Japan's Canon Inc to raise its bid for the firm.
** Vice Media, known for its coverage of current affairs for the Millennial generation, will expand its partnership with Time Warner Inc's premium cable network HBO to include daily newscasts and more weekly series and specials, the network said on Thursday.
** Goldman Sachs and KKR have sold their remaining 13.9 percent stake in German forklift truck maker Kion at 38.15 euros ($41) a share, two people familiar with the transaction said on Friday.
** Slovenia has sold its second-largest bank Nova KBM (NKBM) to investment fund Apollo for about 200 million euros ($216.4 million), daily newspaper Delo said on Friday, citing unofficial sources close to the bank.
** Union Bancaire Privee (UBP) has agreed to buy Royal Bank of Scotland's international private banking business Coutts International, as the Swiss private bank continues to rebuild its asset base in the aftermath of the financial crisis.
** Potash producer Israel Chemicals said on Friday it had made a C$137 million ($109.5 million) offer to buy Canada's Allana Potash, a deal it hopes will accelerate development of a mine in Ethiopia. Israel Chemicals (ICL) already owns 16.36 percent of shares in Allana.
** French energy group EDF is considering whether to take a stake in assets belonging to struggling nuclear power group Areva, business daily Les Echos reported on Friday, citing an unidentified source close to EDF.
** Kenya's Centum Investment has reached a deal with the majority owners of sisal grower Rea Vipingo after a protracted takeover battle between the two sides for the agricultural company.
** Italy's Banca Popolare di Milano is not working with JP Morgan on strategic options, a spokeswoman for the bank said on Friday.
** Just over three months after raising hundreds of millions of dollars in a stock market listing, Japanese mobile game developer Gumi Inc plans to cut 10 percent of its workforce and sell assets as part of a drive to bounce back from losses it expects this financial year.
** Brazil's state oil company Petrobras is exiting Japan due to shrinking oil demand, shutting down its refinery in Okinawa as early as this year and building an import terminal it will sell to another refiner, the Nikkei reported on Friday.
** South Korean steel producer Hyundai Steel said on Friday that it was considering a merger with its steelmaking affiliate Hyundai Hysco, but added nothing has been decided. ($1 = 1.28 Australian dollars) ($1 = 0.92 euros) (Compiled by Rohit T.K. and Yashaswini Swamynathan in Bengaluru)